The Llewellyn crew to watch out for are D.J. Conway, Amber K, Edain McCoy and Silver RavenWolf (fondly known to those who are "ON" to her as Mama $ilver and $ilver RavingWolf). These four authors have probably done more damage to Wicca and Witchcraft than anyone ever has. It's not even a matter of dumbing down witchcraft and Wicca to make it understandable. Mama $ilver is so very obviously in it for the money, she has incorporated parts of Christianity into her "Wiccan" rituals and teachings so that when parents look at the books their kids want to buy, they will agree to get the book because it's as far removed from witchcraft as you can get, even going so far as to make parents think that Wiccans worship the Christian God. She has a "Teen Witch Kit" that she sells, that comes with a pentagram and all kinds of silly, fluffy information that isn't true, and the box opens up somehow to double as an altar. :
Here are three links that explain what I am saying in great detail. They don't just say what is wrong with what Mama $ilver says, they explain WHY it is wrong.
Not ALL Llewellyn authors are this far off-base. The late Scott Cunningham has some excellent books out for the beginner, and while it's not the ultimate herbal, his Encyclopedia of Magical Herbs is a great resource for witches who want a good, BASIC knowledge of herbs, what they are used for, and how to use them.
Raymond Buckland's book "The Encyclopedia of Witchcraft" is a wonderful beginner book, if you keep in mind that what he is teaching is not oathbound Wicca, but good outer-court material that is useful to all witches.
Raven Grimassi is one of the few authors who write about Stregheria (Italian Witchcraft). He tends toward the fluffy, but not as blatantly as the others, and since books on Stregheria are kind of hard to find, he's OK as a source.
Migene Gonzalez-Whippler is a Santerista and has a couple of good books out that touch on the practice of Santeria, however again, it's outer-court material. So while it will give you more or less a good outlook on what's what with Santeria, again there's a lot missing when it comes to the things you only learn when you start progressing through your degrees.
I hope this (especially the links on SRW) more or less explain my disdain for Llewellyn and it's insistence on fluffiness, to the point of not caring about printing falsehoods, just so long as they sell books.