This book has two distinct modes of use, and you should be conscious of which mode you are in.
First-time orientation. If you are reading this book for the first time, read it linearly, chapters 1 to 17. This gives you the full map before you zoom into any territory. Plan two to three hours.
Timed revision. If you have read this book before, you do not read it linearly. You enter from a problem. Something has come up — a design review, a difficult architectural decision, a job interview. You turn to the relevant framework chapter, read the one-line recall triggers, and work back up to fluency in fifteen minutes. The Quick Reference Cards in Chapter 17 make this even faster.
Most of your time with this book will be spent in the second mode. That is by design.