The CWAP book is the best of the CWNP courseware, without a doubt. I would strongly recommend sitting this course if you want to fully understand the 802.11 MAC layer because Devin's courseware is tremendous. He put it together in a way that is logical and that helps someone with a reasonable Wi-Fi background understand the MAC layer in full. To top it all off, it also gives great perspective on using that knowledge to troubleshoot real WLAN problems.
The only thing that it needs as far as an update is information about WMM and 802.11e. If you take the course from a quality instructor, I'm sure they'd update that information when they discuss the chapter on Arbitration and InterFrame Spacing.