Gates of Fire : An Epic Novel of the Battle of Thermopylae
Go tell the Spartans, stranger passing by, that here obedient to their laws we lie.
I read that in the wake of the film "Gladiator" in 2000. The same author also wrote another novel on ancient Greece. Both came out on audiobook, read by Derek Jacobi, the British actor who played "I, Claudius" and also acted in Gladiator.
I pass my books on to others, so I'd have to do research on amazon.com to get the author's name and book titles.