Using Drupal is a great little book if you’re just starting out with Drupal, and want to know which modules could be useful for you. If you’re getting into true development stuff and want to play around with Drupal a bit more, the excellent Pro Drupal Development by John VanDyk would be a much better choice.
This book was written by members of the Lullabot team, who do Drupal consulting and development work. They really know their stuff, so you feel things they suggest in this book (like choosing module x over module y) are worth listening to.
The book itself guides you through typical scenarios you might want out of a Drupal website, like wikis, a shopping cart, workflow, multilingual sites, etc, etc. Each section has some useful tips and ideas, but doesn’t go into a massive amount of depth. So again, great if you’re just starting out and want a flavour of what’s possible.