I came in here to recommend this too. Great book. It's a fictional story that kind is accurate in that it keeps with the known time line of events and fills in all the blanks with a supernatural twist to the whole thing. Quite a scary book, too, as I remember.
I really enjoy the writings of the Stoic philosophers. If you enjoyed Seneca, you should check out Marcus Aurelius' Meditations[1] and Epictetus' Discourses[2]
EDIT: changed the links to Project Gutenberg links on jwdunne's suggestion
I just finished Aurelius' "Meditations" last month - my family has a small, leatherbound copy that was a gift to my great-grandfather for Christmas, 1924. I found it particularly resonant, incredible for a text that's almost two thousands years old.