I received my signed copy of Pro Drupal Development around an hour ago from John K. VanDyk, and immediately rushed to the 18th chapter (on localization), to see how it shaped up at the end. I was helping out with reading the manuscripts of that chapter to help readers get the most realistic view of how locale module helps their life, what are the culprits, possibly bad routes to avoid, as well as side effects of some settings. It was a pleasure to help out on the book, and (as a result) a long time waiting for the book arriving at my house.
I thought I can beat Dries with posting Dries-style photos of the book (evil grin), but just found that he published his usual photo shoot pieces earlier today. Anyway, my photos are up on Flickr for more sharing pleasure.
Being a visual type, I would ensure you that the visuals (flow charts, figures) in the book are very informative, and help a great deal in understanding how things work in Drupal 5. This is a must have book for aspiring professional Drupal developers! To quote Dries' foreword: "... there is nothing that stops you from becoming the best Drupal developer in the world. The only limitation is your willingness to learn."