First off I really do love this concept, and so I'll probably submit quite a few. X3
This book is "Idlewild" By Nick Sagan, who;s one of the sons of Carl Sagan (Awesome astronomer guy).
Here's the synopsis from the back
He calls himself Halloween. He is a unique student attending a most prestigious boarding school-- the Idlewild Immersive Virtual Reality Academy. While his body sleeps, his mind interacts with those of his fellow students under the tutelage of the enigmatic artificial intelligence known as Maestro.
An inexplicable energy surge has damaged the IVR and fragmented Halloween's mind. Convinced this anomaly was deliberately triggered to kill him, Halloween is desperate to recover his memories-- only to discover a devastating revelation about his true existence....
I really REALLY love this book, I actually found the series by picking up the second novel in cassette format (Idlewild is the first of three in the series) for a buck 25. And it was amazing, even better than Idlewild. But if I'm gonna recommend a series you may as well start with the first book, right!?
Anyhow, I haven't read the third book (1st Idlewild, 2nd Edenborn, 3rd Everfree) because according to reviews it was rather underwhelming. Too much of a "happy ending" and I like my series to end on a morose note (I was disappointed Harry Potter didn't die for real, very very disappointed) .
But yes! I definitely recommend! It was very well-written. Lots of intrigue, character development, and it's really rather short, only 273 pages. :3