Rule #1: If the book isn't published by O'Reilly, it's a pile of garbage.
While this rule doesn't always hold true, nearly all non-O'Reilly books really suck. Sams seems to be the worst offender. You can find free online docs better than most of the stuff that comes out of that trash dump.
Anyway, before you shell out $5 or whatever for an awful book, do a yahoo search for "Perl" or something and you'll be suprised how many helpful tutorials you can find. O'Reilly books really aren't that expensive and are almost always worth the extra $20 or whatever. Go to your local Barnes and Noble and you can get 20% off everything.