Lehninger is fine for your course, if used as a referece. Most of my lectures in biochem came directly from Lehninger (in terms of content and figures). However, for review, you would be better off using a review book (I am using Lippincott, and I like it). Lehninger is not geared specifically towards medical education or the board exams. Therefore, it goes into a lot of excessive detail, and doesn't focus as much on the important facts.