(Disclaimer: I write books for SAMS. I've edited them for Manning and Addison/Wesley. That being said...)

Go to a bookstore, get a stack of books on the topic you want. Sit down and read. Spend a couple of minutes on each book, make a "yes" pile and a "no" pile. Really spend the time. If you're going to shell out 20, 30 or 40 bucks it's worth the effort. Repeat with the "yes" pile until there's one book left. Buy it.

Remember that almost no books are good beginner/learning books and reference books at the same time. (most of all Perl books!) They're either one or the other. Make sure you know which you're shopping for.

The style of presentation varies wildly between the books, even between editions of the same book. Pace, tone, language, terminology, and coverage can shift a lot between books under the same publisher, author and even title. Whatever helps you learn, buy that. That's most important with learning/beginner books. Your learning style may not be the same as everyone else's.

Sometimes (especially with reference books) it's helpful to pick a topic that you're interested in or something you've seen online and see how each book presents it. Pick something out of the ordinary like context, threads, closures, typeglobs, strict, or AUTOLOAD; look it up in the index and see which book gives you the explanations you can follow. By picking just a topic or two, you can cross-reference the explanations with each other to find out what authors know what they're doing and which are just bullshitting you.

Every publisher turns out bad books and good books, it's inevitable. SAMS, Manning, Addison/Wesley, and yes even O'Reilly have turned out their share of stinkers.