The Eagle and the Wolves is based on Jack Whyte's A Dream of Eagles series, but that's the only book-based mod for the current version that I can remember right now.
As for total conversions, Timeless Kingdoms and Chronicles of Talera are pretty safe bets. Prophesy of Pendor is another total conversion that's hugely popular, and while the map is the same, for the most part, The Eagle and the Radiant Cross is a very good mod if you like the whole sabre/pike and musket setting.
Some other total conversions are: Britain at War, Britain 1297, Britannia 1080 (it doesn't really have any new items though), Roots of Yggdrassil, Mongol, Peloponnesian War (I think it has the Native map though), Europe 1200, and of course that "old faithful" Hundred Years War.