After reading the first three novels of the Ender Saga, this, as as the finale to the range, was rather dissapointing. Unlike the other books of the series, Ender Wiggin hardly features in this book, apart from the first few chapters.
As the back cover explains, Jane--the artificial lifeform--is able to travel "outside" of space-time. At first this was interesting and exciting, but after the Nth time, it merely became annoying. Also, the book has drifted from the philosophical roots of the previous books, and instead this book concentrates more on the "mystical" and spiritual elements which, again, just became tedious.
If you feel obliged to read this novel due to the high quality of the other books in the series, think twice, for it's not essential.