I have recently discovered a new hobby; writing hopefully mildly enjoyable yet always informative reviews about books on amazon.
I mean, we all--or at least most of us--read those and personally, I usually find a decent critique helpful and I am always grateful for a warning about certain teeny-supernat-romance drivel. Who isn't.
Also, you can be concise without having to bother to follow any proper form apart from what you yourself wish to relate about a book. Reminds me a little of graffiti and those have been popular since...olden times.
And of course, after you read something you really enjoyed, don't you just wanna tell the world about it? That is why, of late, I find myself reviewing and it is much more relaxing than, say, solitaire. Makes me hope for enough time to read that which I can later review.