First of all the premise of Legion is excellent, I really loved it and would like to have seen it used in a full-length novel. The brevity of this story restricted the premise in my opinion, especially as all of Legion's hallucinations were not introduced and we did not get more of a background to Legion himself. The man really is fascinating. Another compelling aspect of the book was the "device" which drives the plot.
The main reason this book is getting 2.5 stars is due to the premise and the the entertainment value. However, I had a really big issue with the religious direction the author chose to take the story. While it would be spoilery to say what exactly leads them in this direction, I will just say that the author had the capability of incorporating ANYTHING from history, absolutely ANYTHING and he chose something religious involving Jesus and in Israel no less. While I can understand to some degree, I felt as though the fact that all of history was available to them made the story wasted on the religious direction. And to make matters worse the author chose to have the bad guys Muslims, apparently from an absolutely terrible group. Sanderson tried to reason this it seemed by noting how peaceful the original group is and yadda yadda but come on, you still made the only bad guys in the book Muslims when talking about a quest for something regarding Jesus. So Islam versus Christianity yet again huh? Wonderful. Sorry, but all Sanderson did for me was point out the absurdity of religion and the violence surrounding it.
I reiterate that this is a premise gone bad and the aforementioned violence and absurdity rather emphasizes my point.