Horus Heresy: Book I Betrayal is probably your best source for all things Sons of Horus fluff related. From their victories in retaking the moon (and gaining the name Luna Wolves) Pre-expansion, to their naming in honor of the Warmaster himself, Horus. The book does a fantastic job of collecting and cataloging a lot of the history, major battles, characters, units, strategy, and tactics of the 16th Legion. There is some more fluff spread throughout the rest of the Horus Heresy series, but the major stuff you seem to be interested in is contained in book I, as well as all the other events leading up to Isstvan V.
If you want actual fiction (novelizations) of the Sons of Horus, JamesY listed the relevant ones.
For the Warmaster! Lupercal!
<--- Sons of Horus player