So today they asked me to review a picture book for the Guide, which is the big book published every 6 months for pretty much every children's/YA title (somewhere in the several thousand range), using a 6 point system very similar to ours here, except it doesn't use half points. Each review is 60 words, so you have to cram a lot into a little paragraph--especially for picture books, where you have to discuss both text and pictures.
Yay! And they even pay a whole $10 per review.
(The Guide is separate from the Magazine, which only reviews the best books. Usually they won't review a really bad book just to say it's really bad--a review in the Horn Book Magazine is enough, usually, to say it's a great book. They might make an exception for a particularly notorious book--for example, no matter how well or poorly they might consider J.K. Rowling's writing, they wouldn't consider *not* reviewing Harry Potter. Not a good example, really, but you get the idea.)