Implementing Cisco IOS Network Security (IINS): (CCNA Security exam 640-553) (Authorized Self-Study Guide)

I have not taken the test yet, so whether or not this book achieves a passing goal for me remains to be seen. But, the section on IPSec could use some TLC. For example, page 392 refers to diagram 5-14 and the "4 ipsec squares" and the diagram promptly shows 5 squares. Are there 4 or are there 5? There's a section on IPSec Framework, a section on IPSec Protocol Framework. What's the difference between the 2 sections? I'm a top down learner and need to start with the big picture and I didn't get that the first time through the discussion on IPSec. I found myself flipping back and forth. IKE seemed to pop up out of nowhere. I'll need to do my own outlining of this the IPSec material, which isn't what I was hoping for. I admit, I'm a newbie and the rest of the book, so far, seems pretty decent, but I don't think I'm going to get comfortable with IPSec based on this alone.