Descartes and Bunce develop primitive notions of databases by using flat files, and they introduce relational databases with careful didactic motivation. The example database used throughout the book contains ancient sacred monolithic sites in the UK and elsewhere, of which Stonehenge is the most famous. The last chapters describe the peculiarities of interacting with ODBC and introduce DBI's Perl-less diagnostic shell and database proxying. Perl newbies with no CPAN experience may find themselves derailed early. Brevity is a large component of this book's wit.
Clarity is the rest of it.
It's quickly apparent that Lincoln Stein and Doug MacEachern spent valuable time writing this book considering the breadth of their subject and the depth they devote to it. The only downside to the book is that it's kind of hard to explain all of the API functionality without assuming a minimum level of competence from the audience. For that reason, this book might be a bit intimidating to novice programmers, but it really rewards you if you put time into it and tinker with things. The book also works well as a source of ideas and inspiration for when you have to write your own server modules, and I'd recommend it if you want to customize your Apache server or speed up your Perl CGI programs.