Have to agree with a lot of the people in the thread and recommend Dan Abnett's Gaunts Ghosts series, love them.
Other series to look out for are the Space Wolves series (first few are by William King) or the Ciaphas Cain series by Sandy Mitchell. Think the Ciaphas Cain series is a lot more fun than the standard noble stuff of the marines as you get to see an imperial guard commissar purely looking out for himself with hilarious consequences .
If you want to read more then here is the wiki:
http://en.wikipedia.org/wiki/Ciaphas_Cain
Other series to look out for are the Space Wolves series (first few are by William King) or the Ciaphas Cain series by Sandy Mitchell. Think the Ciaphas Cain series is a lot more fun than the standard noble stuff of the marines as you get to see an imperial guard commissar purely looking out for himself with hilarious consequences .
If you want to read more then here is the wiki:
http://en.wikipedia.org/wiki/Ciaphas_Cain