I think that would be a really hard book to write. Chapter 7 of Writing Perl Modules for CPAN (free download here) took a mini-stab at it and it was the hardest chapter to complete. It's very difficult to write an even-handed treatment of someone else's work. It's equally hard to make decisions about which modules to include and how much space to give each one.

This may be better done as a series of articles, perhaps modeled after the awesome Perl Advent.

-sam