Right now you probably think you already know a lot about those guys who ran around dressed in sheets. After all, you had to study Greek mythology in school, know all about Greek democracy from Civics, you've seen lots of episodes of "Hercules" and maybe even read some novels in the period, not to mention Bullfinch. You've got a fun idea, and you think it's going to make a fast novel.
I'd read Bullfinch innumerable times as a proto-teen, not to mention Graves and Durant more recently, and studied the period from a standpoint of military science. So when a mention of a single incident in history took over my mind, I knew that research was going to be a quick refresher with a dig only for those little details like city maps and recipes.
If I'd known how difficult it was, I doubt I could have gotten started.
In the course of researching *Course of the Sun* (working title), set in 396 BC, I found that the field of the Classics, which impresses outsiders as both venerable and well-settled, is holey, shakey, and subject to constant revision as writers issue papers championing their view of an issue which is based on a total of twelve potsherds and two thirty-word remarks by ancient authors living four hundred years apart, and speaking different native languages.
I hope my remarks, warnings, and theories here will make it easier for you to reconcile your research pieces with each other as you head on into this period.
Most of the easy, introductory books are misleading in the extreme in that they paint the Greek world as an homogenous culture. Things like military organization, citizenship limitations, and marriage customs varied from one city to another, sometimes drastically. You must not look at this as studying one country, Greece, but many countries, Athens, Sparta, Thebes, Argos, Elis, etc., not to mention the overseas Greeks from Central Asia to Marseilles (originally the Greek city Massilia). A parallel would be studying North America when it is still a hodge-podge of European colonies of Britain, France, Spain and Russia. On top of this, customs in a city-state can vary according to wealth, status (citizens are always a minority), rurality, and religion.
As I was dealing with the Spartans in the Peloponnese, I quickly realised the fact that most books are also absolutely Atheno-centric, and usually Atheno-philic. This is because the Athenians loved to record their wonderful accomplishments, and would even support grants to foreign writers like Herodotos to write about them. The Spartans, on the other hand, actually made it illegal to write down their laws, and felt their deeds spoke for themselves. The most abundant and easily found information is Athenian, which is why most Greek historical novels seem to wind up there. It's the easiest to research.
There is also often a double-filter of Athenophiles between you and the period. The Romans, another lip-service democracy ruled actually by cliques, greatly promoted the Athenians as their new culture-masters after they had destroyed their old ones, the Etruscans. As well, the study of ancient Greece in English really only picks up in the Victorian period. Before then, the price of the Elgin Marbles, the Parthenon frieze, was knocked down because they were merely Greek, which everyone knew was just the simplistic predecessor of the really valuable Classic sculpture, Roman sculpture. Victorian Britain created an Athenian mirage, seeing the distant nation with its limited democratic representations, conquered empire, reliance on sea-power and slave labour, and thorough home sequestration of all proper ladies, as "Britons in togas" (please note that Greeks didn't wear togas, the distinctive dress of male Romans, but I have seen the phrase more than once). They usually equated the Spartans with the hated parvenu nation of Prussia, and propagandized accordingly.
In short, keep that grain of salt ready by the handful when reading. Exert a little scepticism, keep your options open, and question authority.
Your best bet is the two-pronged attack of reading ancient authors and very recent archeologists reporting on sites. I cannot recommend reading the scholarly Classicists on culture without a full bag of salt, and after you have read the ancients for one big reason:
That's a thousand years, in an area that knew numerous internal wars and exterior conquests. The assumption is always tacit, never verbalized, and I swear most of these "careful scientists" never realize it *is* an assumption behind most of their work. The assumption is ridiculous, when you look hard at it.
Take the constant arguments about the reliability of the ancient authors on whom they base their history. Xenophon and Plutarch absolutely and completely conflict on the matter of Spartan sexuality. Plutarch says that all boys have adult male lovers, and that matrons think nothing of declaring their love for this or that maiden. Xenophon says that the Spartans did not isolate men from boys, the extreme to which some Greek states felt impelled to move, but that the Spartans loathed pederasty as they did incest between brother and sister or parent and child.
The currently dominant proponents of "Spartan institutionalized homosexuality," who are building careers examining every institution, ritual, and relationship in the entire history of Lakedaemonia in terms of who buggers whom, of course say that Xenophon was a liar. He can't be misinformed, because he lived in Sparta for years, and fought alongside them in their wars against his native Athens. He was, the Classicists say, a homophobe, who lied about the open, blatant, universal Spartan homosexuality because he admired and heroized the Spartans and simply refused to impute a behavior he hated to them.
Let's conduct a quick reality check.
Think of any homophobe you know or have known; let's call him Red. Imagine that he has two young sons. Now Red "knows" that British boarding schools are a hot-bed of homosexuality and pederasty, and that any boy sent there will probably be gang-raped in the first month. At best, the boys grow up in an atmosphere where pederasty is acceptable and encouraged, even if the level of education is high. So does Red send his precious sons to one of these sinks of iniquity? Not hardly.
Yet Xenophon sent both of his sons through the Spartan educational system, when he could have sent them to Elis or Argos or educated them at home. So either Xenophon was not a homophobe, approved of his sons becoming minions, and had no reason to lie about the Spartans, or he was a homophobe, and sent his sons where they would have the least exposure to pederasty as a way of life, proving by his actions that he did not lie about the Spartans.
What the Classicists are presently ignoring is that Xenophon wrote about 350 BC, but that Plutarch wrote after 75 CE, nearly 450 years later. If this is not enough, in between, the Spartan Lykourgan way of life was broken, outlawed twice, and revived from uncertain memories. Moreover, most of the Spartiate lines on which old Sparta was based were extinct. Most of the Spartans of Plutarch's time were the descendants of the helots, the serfs of the Spartiates, who were enrolled as citizens by Nabis.
Let's draw another parallel with our own experience.
You read an account by one writer that San Francisco is a town where a publicly homosexual lifestyle is not only acceptable, but even fashionable, and that there is a larger percentage of homosexuals in San Francisco than in any other city. A second person writes that San Francisco is a city where any such queers would be immediately ostracized by anyone not completely degenerate (as they obviously are), and the rare one appearing will be lucky if he is only ridden out of town on a rail without being tarred and feathered first.
Which is lying? Neither. One writes in 1890, the other in 1990, and I'll bet you can tell which.
To back up Xenophon, Aristotle, writing in the same century, in his Politics (1269b), specifically states that the Spartans "were under the sway of their women," contrasting this shameful state of affairs to nobler cultures "as have openly held in honour passionate friendship between males," as he says the Spartans specifically did not. So according to a great supporter of homosexuality, the Spartans were homophobic as a culture just as Xenophon also claimed -- in these earlier periods.
In short, it is perfectly possible that at one period the Spartans were all raised to be homosexual or bisexual, and annually beat a couple of boys to death at the shrine of Artemis Orthia; while much earlier they were relentlessly heterosexual and held nothing rougher at the Orthia temple than to have a ring of men with switches through whom boys dodged to steal cheesecakes from the altar.
But the Classicists, because of academic fashion, ignore this temporal division of culture.
So, whether you had planned on it or not, you will now get to read Great Classics, like Herodotos, Thukydides and Tacitus, because when you get to the moderns, you must know from when as well as where their information comes. Classicists can be so diametrically opposed, that you really have to read the raw data and interpret it yourself.
You may find it far more fun than you expected, depending on the translator. A Victorian who Latinizes names and "thee and thous" and uses his native circumlocutious language is a complete sedative. A modern translation is often the best reading you can get on the subject.
Still, it is difficult to take the ancients without interpretation. As Stephen L. Glass writes, "The inescapable truth is that a large portion of such evidence as we have [the ancients] is disconnected, late, uncritical, relentlessly anecdotal, or usually all four at once. It is in the face of these odds that our use of such evidence is understandably, if amiably, capricious." ("The Greek Gymnasium; Some Problems").
Plutarch, on whom so many Spartacists rely, was only a compiler of earlier writers, whom he often mentions by name; this air of scholarly research makes him familiar, "one of their own," but his information is often so internally inconsistent that it must be wrong. The writers who contradict him are far more cohesive and believable.
Herodotos, like the Old Testament, often repeats a good folk-tale twice, say, with different kings. Xenophon was writing from memory decades after the fact, without notes, and understandably misses a campaign here and there, besides purposely refusing on occasion to mention someone he loathed, so that posterity will *not* remember him.
So, yes, you still should read books by modern scholars on the period. Just remember: when they're not talking about what's been dug up, the Classicists have no better sources than you do. If they refer in footnotes to an ancient author, go read the original. The original probably discusses side issues useful to you, that would be considered unnecessary digressions in the Classicist's paper. For example, everyone quotes Thukydides about the war he helped fight. No one mentions how in his introductory matter he states that only in his life have the Olympic Games non-equine events been conducted completely in the nude, and that not so long ago, Athenian men used to wear golden dragonflies in their hair.
Again, this is not the world that the YA introductory books present, where all sports have always been done in the nude in monolithic ancient Greece, and men always dressed plainly in white, with no girlish jewelry at all. The funny part is that the severe Classicism they describe was not Athenian, but part of the Spartan fashion.
Based on my experience, the best thing you can do is to read far more widely than you think you will ever need to, think hard about what you do read, and reread the best books several times while you work. Each time you will carry away a new level of interpretation and clarity.
History will always hand you more than enough authentic incidents for a novel if only you read enough of it, and not just the same skim-the-political-surface book by different authors. Dig deep, and you will be repaid for your hard work by a clear vision of a place and time, a society, very different than ours, very exciting to explore once you realize how foreign it is. The urge to show your reader all the fascinating tensions and dichotomies you have figured out will keep creating incidents in your mind, new incidents, not just the same old melodrama in sheets instead of bustles or farthingales. Your novel will be one OF ancient Greece, not just pasted on the setting.