It is a kinda cool idea. But I think a lot of people overlook the fact that book covers are designed for you to judge the book on. I mean, some poor artist (I presume) spent aaaages designing that book cover channeling it through a dozen meetings with editors and other graphic designers etc for you to judge that book without having to read the whole thing.
Show book covers a little respect, please!
I have a very specific type of book that I like to read so when ever I see these things I just think "who would want these? I know Tumblr users wouldn't they only read Harry P., Lord of the Rings, and Percy Jackson."
Show book covers a little respect, please!
It's something cool and original, don't make such a big deal out of it.