I give workshops on Adobe Acrobat to university faculty and staff, and I'm always asked for recommendations for a book on the topic. As far as I'm concerned, this is the ONLY book for beginning and intermediate Acrobat users. Adobe's Classroom in a Book, which could have been such a good idea, is riddled with errors (including errors on the CD that were there in the version 4 book), not very well written, and costs more than twice as much.
Jennifer Alspach has done a great job of taking a difficult, complex subject and making it interesting (and even fun, occasionally). The organization of the book is just right, and the topics are thoroughly covered. As an author, I also appreciate the nice layout and design and the high production quality from Peachpit Press. This is a must-have book if you are interested in Acrobat!