Depends on what you mean by "demon."
I mean, I'm putting in everything I can find a decent amount of information on. So far, I have (demon wise), the Chiang-Shih, the Pishacha, the Rakshasa, the Oni, and some other strange creatures (still trying to pin down the Kuei...).
The book will also have dragons, serpents, ghosts, ghouls, vampires, 100-foot-long centipedes, foo lions, 700-mile-long catfish, flesh-eating horses, fish-elephants, flying heads, shape-shifting sorcerers, and beastmen.
Oh, and one enormous [deleted by sysop].
Oops... Guess you'll have to read the book to find that one.