Practical mod_perl is a doorstop sized volume that provides more information on using mod_perl than you ever thought you needed.
The almost 900 pages are divided into five parts and a bunch of appendices. Part I, "mod_perl Administration" covers building, configuring and installing mod_perl, followed by some Apache details and an 80-page guide to coding with mod_perl in mind. Part II, `mod_perl Performance' deals with ways of getting the best out of Apache and mod_perl, with a little about security. Part III deals with databases, including persistent connections and data sharing. Part IV is a great guide to debugging and troubleshooting. Part V is a brief look at Apache 2 and mod_perl 2.
The appendices are useful. The first is a short section of around a dozen small `recipes' for performing various tasks using mod_perl. I found these a good base for more complex tasks, particularly when combined with examples from elsewhere in the book. The second is a list of Perl modules that extend Apache and mod_perl with a brief description of each. The third gives some strategies for providers wanting to host Apache with mod_perl. The fourth and fifth give good overviews of the Template Toolkit and AxKit, an XML application server built on mod_perl.
The book is readable, tending towards heavy writing and certainly dense, but I didn't feel this was a problem in a book meant for a fairly advanced audience. I think you'd want to be a fairly good Perl programmer and well versed in Apache before needing this volume and shouldn't expect to be spoon fed. I thought it well written.
In a book of this size you expect to find a lot of example code, and you won't be disappointed. The book is peppered with short Perl examples and example command lines and configurations, all well explained. The one shortcoming is that there aren't many examples of full-blown applications where you can see everything discussed and have it explained all in one place. I would have appreciated some more of this, the examples tend to be on the short side.
This book sits well in the marketplace. It provides more details on running, installing and configuring mod_perl and Apache than mod_perl Developer's Cookbook (and also delves more into the reasons for doing something one particular way and much more help on debugging), though the Developer's Cookbookbecomes a good companion to this volume as it provides a lot more in the way of examples. For those that want to get deep into the high end of mod_perl there is Writing Apache Modules in Perl and C, which is at core a good book on high end mod_perl programming.
O'Reilly have their usual website with Table of Contents, an example chapter, and errata. The authors have their own website with some of the same information and all the code examples from the book as both individual files and one 40k tarball.
I would recommend this book to anyone who administers and writes for mod_perl, it fills the missing pieces in mod_perl Developers Cookbook and is a good companion volume to it.