People, you all left out what is the most important aid for the busy grad cramming in a ton of books...Read a couple book reviews of the book(if available). U cant base a criticial review of the book or even an entire discussion for a seminar class with this tactic (well I have but I dont recommend it!), but they (the good ones) outline the main points, put the book within the historiography, etc..
It is also not a dumb question. I myself read the intro twice, slow, and the rest as fast as I can while taking notes in the book(underline/margins). The goal of my notes is to be able to review the book using the notes in 30-45 minutes, so far it has not failed me. Reading slow is sort of pointless, because you are not going to remember every sentence you read...the faster the better for me!