Build a mental map of where to find things, and then refer back for details as needed:

1. Skim the whole book. The goal here is to learn basic concepts, keywords, and the structure of the book.

2. Start coding, refer back to the book as I encounter things I don't understand.

This works better with paper books, because it's easier to remember where I saw something ("upper corner of left-hand page next to diagram, towards the end of chapter 10").