I read this story fast and found it interesting and cool. I was a bit hesitant at first, since I didn't see how a man's hallucinations could possible serve to help him solve mysteries, but Brandon Sanderson makes it work. In addition to the cool character, he introduces a really cool piece of technology: a camera that can take pictures of the past. The whole plot revolves around it being stolen and the implications of how it can be used. Makes for some very good discussions.

A longer review is available on my blog: strakul.blogspot.com/2012/12/novella-review-legion-by-brandon.html