This is from an advance review copy for which I thank the publisher.
Translated from the original French by David Warriner, this book (curiously originally titled Arriba el Sr Flat!) was a bit young for me, so while I found it entertaining and I recommend it as a worthy read for middle-grade readers, it's also the start of a series, and I don't intend to follow it beyond this volume. I'm not much of a series kind of a guy!
So Alex is a middle-grader who is totally irresponsible and I'm not completely convinced that he learned his lesson by the end of the book! His room is a mess and his homework assignments - while he does them - do not get turned in. Frankly I think his teachers are as irresponsible as Alex is if they don't require the kids to turn in their assignments regularly!
Alex discovers that this plush toy he finds (which he calls a 'stuffie') is actually a real monster from a book (so the monster claims). The monsters all got kicked out of their book by the evil Dr Brut. The monster, Mr Flat, brings a change to Alex's life by interesting him in reading, but aside from Mr Flat going missing, that's about all that happens in this short novel.
The novel is illustrated by Liliana Fortuny, and has some comic-book like pages, but mostly it's a chapter book and it's mildly amusing and entertaining, and the pictures are sometimes funny, so I consider this a worthy read for its intended age group.