As a 23 year old, I can tell this book was meant for younger audiences than I. I've been told that this is a common book that many school students are forced to read. However, I was never forced to read it, which may have something to do with why I enjoyed it.
Although many of the antics of the youths in this book are a bit silly, I found the fart jokes and petty remarks bearable. In the foreground, there's a remarkable tale of a boy trying to overcome his peers and the various challenges put to him by adults. However, the background tale intrigues me more and I find it to be an incredible tale of how a great many adults manipulate the future of a single boy, barely a teen.
I usually dislike books and series where a single character is "The Chosen One" and is the only real hero of the book. Despite that point, I think Ender's Game is a reasonable display of the complex scheme surrounded by his choice. The choice to make him important was based of many years of research of children; mental patterns, social interaction and various teachings.
There is a reasonable display of character development, but many characters are lost and found in the many times he changes units and classes. Some, from the start of the book are "lost" and never mentioned again and other enjoyable characters are "lost" at various points throughout the chapters.