Complexity, language, and word count. It really is a thin line sometimes though. I went to my library and took out a ton of books that I knew were one or the other, but had to guess which one.
If you go to the Writing For Kids forum, there's a thread on RenLearn with a link to the site. It's for teachers to find quizzes for books, but it has a huge collection of book info and it includes word counts and target grades for different books. You can kinda figure it out from those two things. Word count is huge, but I definitely decided some shorter books were low MG after reading them.
Roald Dahl and Beverly Cleary books are low MG, but I thought they would be CBs before I read them. I could see the difference between Beezus and Ramona (LMG) vs. Clementine (CB), though, even moreso after I typed out each one's first chapter.
If you go to the Writing For Kids forum, there's a thread on RenLearn with a link to the site. It's for teachers to find quizzes for books, but it has a huge collection of book info and it includes word counts and target grades for different books. You can kinda figure it out from those two things. Word count is huge, but I definitely decided some shorter books were low MG after reading them.
Roald Dahl and Beverly Cleary books are low MG, but I thought they would be CBs before I read them. I could see the difference between Beezus and Ramona (LMG) vs. Clementine (CB), though, even moreso after I typed out each one's first chapter.