In the way that any sentimental book about childhood and becoming real (cf., Peter Pan, Pinocchio, The Velveteen Rabbit) is much more appealing to an adult audience than a young one, I wouldn't actually recommend this to any kids. I enjoyed it, and I really empathized with Jacques' dilemma. And of course the ending brings it all together in a meaningful way. But I think kids are going to read this and think Foster's Home for Imaginary Friends*, and wonder "why bother?"
*Feel free to substitute some other, less dated reference, that I don't get because I am already too old.