I loved Leviathan! This is one of those rare YA books that really embraces its own category. Deryn and Alek feel and act like teenagers, and I wouldn't have it any other way. I think it will resonate most with readers age 13 to 17, as well as older fans of YA steam punk or sci-fi. I wouldn't hesitate to give it to a reader as young as 10 or 11 if they showed interest, as the content is never graphic.