A few years back I had a lot of free time on my hands and read a few of the THE HORUS HERESY books. I loved them!
Now I've gotten back into gaming I've read a lot of fluff about the drop site massacre but I want to learn more about it. Are there any books that cover these events?
Might get a few more responses in this section
AFAIR, only Horus Heresy novels such as Fulgrim
and The First Heretic
cover the Dropsite Massacre in significant, there-in-the-moment detail. From the perspectives of the Emperor's Children/Iron Hands and Word Bearers respectively.
There's also a whole bunch of novels, novellas and shorts, both written and audio, that flashback to or reference the battle, providing a wealth of perspectives from the Salamanders, Raven Guard, Iron Warriors (?), World Eaters etc.