I don't read a lot of light novels, but Zaregoto is good. The first volume is almost a like a classic detective/crime novel, but the second one is much more original. Vol 2 is here, 3-4 here and I remember seeing links for scans of the English adaptation of the first one on /a/, so they must be in the archive.
From Kamachi (Raildex), I'm reading The Zashiki Warashi of Intellectual Village, and find it better than Index. It's a mix of mystery, youkai stories and a bit of comedy. It's all on baka-tsuki.