Yes, there is a difference between the books. Some are bad, some are good, some are better. You might find some helpful information in the Book Reviews section. For my (unworthy) two cents, I'm with everyone else who says buy an O'Reilly. Get Programming Perl if you have previous programming experience. Get both Learning Perl and Programming Perl if you don't. (I say to buy both because you'll probably outgrow Learning Perl eventually.

-sauoq
"My two cents aren't worth a dime.";