I've got the same problem with finding decent content in Aozora Bunko. For me, the main issue is how to find content which matches my level (actually being interesting being the other problem, but seemingly harder to solve).

I set up a really hacky "grader" algorithm and run it on a bunch of the Aozora Bunko books, then put them online [1]. The very "easiest" books are kinda boring, but it is certainly easier finding usable material in that list than looking in Aozora Bunko itself. The one I've found most interesting so far is 銀河鉄道の夜 [2]

[1] http://www.readyourgrade.com/

[2] http://www.aozora.gr.jp/cards/000081/files/43737_19215.html