I start reading it 'cause the anime is really great!
For information, the anime cover the first 3 volumes, and it's pretty accurate. You could easily start reading the 4th without loosing anything.
there's 10 volume with more or less 200 pages.
I'm in the middle of the fourth now so I will update this review when I'll be finished. (that will surely take some times cause i already have other stuff to read)
This is my first time reading light novel, maybe it's me, but there something about the layout that feel kinda strange compared to a "genuine" novel.
still it's great but I can recommend you enough to watch the anime