Interesting book, I bought it to propose it (or part of) my students. I love the imagination of two kings Being and Having to understand these famous auxiliary, so great. However, I find that Hugo has too easily explanations brought to him, the arguments seem already knew, which I find, removes credibility to this item ... The structure itself sometimes is not clear (this is especially a shame when you know that the target audience is children): dialogue and narrative are mixed. One last point that seems important to me: the part called "a traitor to unmask" troubled me to understand because if the granting or not, Hugo asks this "my sister is bought candy." question: "Who Who?" and he deduced that the traitor is here to unmask Have. He exclaims that he understood, but how? In no way have the verb is used ... In short, it is a very useful book, I loved to read as an adult, but I think it necessarily be an adult with a youth the bed to specify certain things to him because some elements are laid as obvious as not.