I don't get many comp copies but the last ones sent really made my day. I don't know if he is a new hire or not but Fantasy Flight's Kyle Hough went the extra mile to make sure that I got some comps for artwork I did last year for FF's Call of Cthulhu CCG and A Game of Thrones CCG. The guy even sent a hand-written note...so kudos to FF and Mr. Hough for staying personable with freelancers.
Scans of the card art comps can be found below:
http://www.flickr.com/photos/simpsonflickr/3718656486/
http://www.flickr.com/photos/simpsonflickr/3716245984/
I hadn't read the AGOT series at the time but I've read and re-read everything Lovecraftian since grade school.
Largely what an illustrator will get is art direction, some references for style, and possible excerpts dealing with climax and story arcs (what most book covers entail). If a deadline permits it, then I might go to the book store or library and get more of a background feel of the intellectual property that is already released. As an illustrator, you don't want to be waist-deep in a painting to find out that the type of dragon you just drew wings on lacks wings in the books.
simpson