But flindophile is right on when he suggests either Clinical Micro made Ridiculously Simple (a must have) and/or Levitson and Jawetz for Micro (and Appleton and Lange book). Both are excellent reviews, easy to read and appropriate for course and USMLE work.
I'm a big fan of The Immune System by Peter Parham. It's concise and easy to understand. It even has glowing reviews on amazon.com. Also, it's paperback.
check it out, i know most of my classmates like it too.