Well, this is the way I look at it:
1) Books and magazines become outdated VERY quickly. Some information that was Godspeak 3 years ago is now ridiculed and thought of as utter nonesense. On the other hand, reading this material objectively lets you interpret it in your own way and sometimes make excellent deductions.
2) The Internet is fast and holds a TON of information, although it sometimes translates DIRECTLY from the aformentioned books. You still have to take it with a grain of salt, but at least its free and easy! (My favorite kind, ha ha!).
3) Pet Shops? Ummm.......yeah........... (that's about as sarcastic as I could possibly type!).
4) Breeders. VERY good source of info as they've "been there and done that"! Only trouble is, some are a$$-heads and don't always share their discoveries/secrets acurately. Also, they don't let you interpret. They make you think THEIR way. If its worked for them, then it must work for everybody. So in a way, its less educational that reading the outdated books. Ha ha. Its not all bad though, most breeders are great and are just happy to talk about their passion!!
So yeah, my answer would have to be a combo of #'s 1,2, and 4. Depends on the animal in question as well. I mean, if I had a query on monitor husbandry, I wouldn't exactly look in a book as most of what we know has surfaced in the last VERY short while. Just an example.