Summaries and back-cover blurbs never capture a book in its entirety. They are meant to be the hook with which to draw you in. And while the hook for Ender's Game is great (A six year old saving the world: how much better can you get than that?), the ensuing plot and story is even better. Ender's Game is rich and layered, building slowly to a crescendo.
While it's nicely layered and realistic, Ender's Game is not a book that you need to be an English professor to understand. It says what it says plainly, but does it extremely well. Psychology plays a large part in this novel: what do war games, living and breathing fighting, do for young children? For that matter, are these children children at all? Orson Scott Card raises big questions and he's not afraid to hit them head-on.
This book is very well-written. The most surprising writing element, noted by even the characters themselves, is how they talk. This is not a novel about children. This is a novel about young adults forced to take on an adult's role and responsibility in a child's body. So much of the feel of the book is one of talking between adults, not children.
Because these weighty topics are hit head-on, the book has its own share of darkness. Ender kills two children before he is twelve years old. The characters swear when they must. This is an adult book about children, not a young adult novel or anything of the kind. Young adults will definitely appreciate it, and get a lot out of it, but it's not going to be watered down to be 'acceptable' for their level.
Ender's Game is a great read for sci-fi fans, but its weighty topics mean that it will be better appreciated by older teens and even adults. Card's intensity and willingness to butt up against tough issues also give it a very powerful message that is plainly apparent to those who are ready to listen.