I picked this book up because it covered memcached, which I'm not familiar with and wanted to learn, as well as Apache, MySQL, and Perl, all of which I know very well, but I like to see other people's views and practices. The book is fairly modern, I had bought it in 2010, and it covers object-oriented Perl and, I was surprised to discover, Moose (the latest Perl OO framework).
Although this book is not the last book anyone interested in any of the topics will probably buy, it certainly will allow developers not familiar with the technologies to get a good grasp of the subjects, and more importantly, put it all together from beginning to end. I think that is probably the most important aspect of this book.
Armed with only this book, since everything covered are open source technologies, a user could dive deeper into any subject with just web searches. So maybe it is the last book someone would buy on the LAMP stack.
I initially tried to follow the examples and methods to implement a product but found that routing had changed substantially with release 3.0. I still refered to it for some techniques because it was dived deeper than the updated version written by someone else.
This won't help much if your dealing with the recent releases but would be useful as a reference for those items that hadn't changed with release 3.0 and beyond.