I, personally, wasn't extremely fond of this book, being a 13 year old female. I loved reading Ender's Game and I was hoping for a similar experience what with the Indigo 8 training academy for space fighting, etc. Of course, I also read Ender's Game in 3rd grade and I was expecting a more YA-aimed book. This book strikes me as very much middle grade, more specifically for boys in middle grade, I would suppose, though Kaylee provides a very present character for female readers. I think one of the main things for me as an 'older' mind rather than the more intended middle grade audience was that the beginning of the book felt rather like a collection of tied-together drabbles, almost, if you are familiar with the term. In the first chapter or so we just had - boom, page where the warp glove comes in and - boom, another single page and he's talking with Danielle and - boom, this one page of him in the training simulator under the garage. Despite how we had several moments tied together, presumably to help give us a taste of the world and what is to come, it felt rather slow to me. Later, the action definitely picks up, though I really think the closest comparison of how I see this book is like how I see the new little kid shows on TV. Being 13, I really see how all of these things in the TV shows just don't quite work or shouldn't be so - the kids not knowing graphs or how much a dime is worth even though they are 12 years old in the show. For me, this came through in how new characters gave up information or trusted the main characters so easily and how, miraculously, the three other alien felons accompanying Skold, Zachary, Kaylee, and Ryic all ended up dead before any of the three trainees did - and why would Skold keep all three of them along when he only needed one of the three as a hostage/leverage/warp glove access?
However, the book was well written I think that any middle grade reader would have very much enjoyed this book - I'm simply not the right audience for it. On the other hand, I feel anyone reading above middle grade would not be so enraptured by it. If you are looking for a similar, more adult/YA intended novel, I would recommend Ender's Game. This book almost seems like a younger-aimed version of Ender's Game to me, and could even have the basic plot be translated into a Star Trek episode. So, I would have to say well done and well written to the authors, but I feel that once a person passes middle grade, this book will not be so popular with them.