This whole Harry Potter thing has largely passed me by, but I sat in amazement and befuddlement as the girlfriend devoured the whole thing in about 4 hours yesterday afternoon and sobbed through the last 50 pages or so.
At which point she went back to the beginning to start over, and re-read the first half b/f bed.

I'm just starting
Only Revolutions by Mark Danielewski, which, at the very least, looks very interesting. It's a rather unique format: each page is divided roughly in half, and each half has text printed facing in opposite directions ... that is, the book can be read with either cover serving as the "front", and each page has two sets of page numbers (one if read in one direction, the other in the other direction). Perhaps predictably, the two versions are told from two separate points of view, and the whole thing is set up with a roughly palindromic structure.
I'm starting it w/ a bit of skepticism, as it seems just a touch gimmicky, but ... the language is interesting (a strange kind of not-quite-poetry (several of the reviews I've read suggest that there's an implied connection w/ rap?), with lots of typesetting and formatting tricks), and I'm told that once one gets used to the format (and the opportunities to flip the book upside down and read back in the opposite direction), the story is quite lovely. And it's gotten wonderful reviews, if that means anything. Why all the o's and 0's are brown in one direction and green in the other is beyond me.
I'll report back after I've finished ....