I try to write down a few thoughts on every book I read whether I liked it or not. I find the process helps me appreciate the books better and, possibly, scratch the surface of just why I like some and dislike others. It also makes me read a little more critically; some might feel that could detract from the enjoyment of the story but I find it enhances my enjoyment of a good story and makes me more willing to give up and avoid wasting my time on a bad one. Posting these thoughts in the Chrons Review forum sometimes results in some discussion with others which, again, is something I enjoy and, particularly in the case of a good book, can extend my enjoyment of the book over a longer period of time.
I rarely actually recommend books; I'm acutely aware that when it comes to books it really is horses for courses. I don't say I never recommend books, just rarely.