So on advice from this thread a few pages back, I have skipped over Fulgrim and instead read Descent of Angels.

It was pretty bloody awesome. It did have very little to do with the horus heresy itself, spent almost all of its time setting things up for heresy, but I quite thouroughly enjoy it as no other book at this point had gone into that deep of an investigation into how pre-imperial-contact worlds were, and did an awesome job showcasing the societal impacts of compliance, the Astartes, and the arrival of the Emperor.

I had fun with it.