When I got this book, I was surprised at how small it was. That's not always a bad thing, however. It is hard-cover, which I just don't like. I like softcover books because they fit in back-packs better and usually keep the cost lower. Oh well, now to the content.
As an experienced PHP programmer and flickr user, over 1/3 of the material was easily skimmed through. There is an intro to flickr, and an intro to PHP. Then the authors take you into actually registering for a Flickr API account and you can start access photostreams.
All in all, it was a very fun to work thought the examples and start modifying them on my own. The work with RSS/ATOM was quite fun and not something I do on a daily basis, so having the text on hand was nice.
The only downside to the book was that there is very limited exposure to the real Flickr API. Most interaction with Flickr is handled through a PHP-pear library/application named Phlickr. It works quite nicely and is maintained by one of the authors, so it is understandable why this was chosen. I do think a little more interaction with the vanilla API probably would have helped though.
If you are into media-driven web design and social site integration, this a fun book to work through.