I have a short book review in the current issue of C&I:
Chemistry & Industry No 21 (10.11.), 30
review of "The ubiquitous roles of cytochrome P450 proteins" by A. Sigel, H. Sigel, and R.K.O. Sigel, eds.
While this is a technical and horrendously expensive book (not to mention part of a series), I really enjoyed reading parts of it. This is because as a protein researcher I've often come across P450s but never understood a thing about them, so here at last all the questions I never dared to ask were answered in a comprehensive fashion.
Essentially, the secret behind their confusing multitude and variability is that the reaction they catalyse leaves a "spare" oxygen atom, with which the different members of the family can do all sorts of different oxidation reactions, so this is why there are thousands of them.