[Captain_Loken]

Definitely read the Horus Heresy Series in order. Remember, these are based in the year 30K when our beloved Emperor was still walking around, kicking ass and taking names... then he ends up as a vegetable (but that is a whole new story). :angry:

All the rest can generally be read as and and when as they are generally 40K.

Just remember that if you happen to read damn near any of the Chaos books before finishing all 60+ Horus Heresy books, you will know how it ends and what Brother Emund means.