I have to confess it's a long time since I read any Judy Blume, and I don't think I ever read Blubber before. It's good - the main character takes part in bullying one of the girls in the class (who isn't even particularly fat but just never fights back) and towards the end she finds that she's now the one being bullied. From a writer's point of view it was really interesting to see how the main character was portrayed - it's very difficult to write from the point of view of a bully because you don't want your readers to hate her so much that they put the book down. I thought it was briliantly handled until the last few chapters, when the attention is turned to a new victim. This seemed to fizzle out rather quickly, and the main character didn't have any kind of realisation of how nasty she had been in the past. Maybe I'm being naive, but I'd have liked her to have some kind of moment when she realised that 'what goes around, comes around' and all of that.
It's a fast read though and suitable for children at the middle/top end of primary school. I should think too that it would provoke a lot of discussion.