This year we're using Baynes & Dominiczak Medical Biochemistry from Elsevier Mosby, 2nd edition. However, the biochem department at KCOM does an excellent, excellent job creating note packets/handouts from each lecture. Many if not most students simply use those. When occasionally they need to double-check something in a book they just check it out from the library.
Our official book this year was Mark's Basic Medical Biochemistry which should be renamed Basical Medical Crap, I used Lippincotts instead to supplement the notes and found that the best.