There are a number of big differences between the two, although both are excellent.
1. Q-book has its sets of 50 questions organized by subject: Phys, Path, Biochem, ect. This is different from q-bank where you take tests with questions from all of the basic sciences (as prep for the real thing).
2. The total number of questions is far fewer for the book, which is about 450 pages or so. Q bank has somewhere around 2000-2500 questions but Q book probably only has around 500 (I'm making a rough guess.)