It's pretty rare for me to read a Drupal book that I can't recommend to anyone. So rare, in fact, that this will be the first time I've done so while reviewing books for DrupalEasy.
Before I go into details, I want to be clear about something: writing a technical book isn't easy. While I haven't written one myself (unless my Master's thesis counts), I have written my share of technical articles and I'm never surprised at how much longer it takes me than I originally imagined. This is mainly due to the difficulty to make my thoughts clear to a large group of people. Combine that with a topic as difficult as the Panels module and you've got quite a task ahead of you.
While the idea behind panels is easy to grok, as the saying goes, the devil is in the details. Earl Miles (merlinofchaos on drupal.org, and one of the very few to score "11" on CertifiedToRock.com), the creator of panels, has stuffed every conceivable option and an unbelieveable amount of flexibility into the Panels suite of modules. As with many things in the Drupal community, this makes for something very powerful, but also something very time-consuming to fully understand and use - both in theory and practice.