Yeah, I'm talking about the novels. Not the manga. There have been various manga versions  brought over already. I think one may have even originated in the US, but I'm not sure about that.
All text...well, there are some manga-style pictures, but less than 10 in the book. This is pretty typical for mass-market serial novels in Japan.
The TOKYOPOP version is scheduled to hit the streets in September. Pretty quick for a novel compared to other publishers...
I didn't watch the whole first series but I do remember cracking up the times we watched it at Brandon's place.
About the books, they're not earthshaking great literature or anything. If you laughed at the anime you'll probably laugh at the books. They're short. Very short, actually--around 40,000 words.
The slayers world has some interesting cosmology, but not much comes through in the first book. It barely hints at future events. It also has an interesting magic system which isn't explained much at all in this one either. The rest of the world is fairly standard role-playing fantasy fare.
It's got some funny characters though. Oh, and the books are all written in first person from Lina's point of view. And there's a fair amount of "talking to the reader"...something to be aware of if you don't like that sort of thing. But the reader she's talking to seems to be someone from her universe rather than ours.