Rebecca found a nice site called http://www.goodreads.com/ where you can load up the names of books (searchable by author, name of book, etc.) you have read and rate them. I played around with it for a few minutes, loading up about 200 books (not hard if you read the entire output of some authors and every book in some sectors), and then looked over to see what Rebecca and Dr. Hypercube were reading and made a list of what to read next, putting "A River Runs Through It" at the top. This should save some time at the bookstore.
Despite my legendary cheapness, I buy books and do not go to the library for them. Perhaps this is not smart, but I like the comfort of books and I like being able to look things up (though the Internet has made that a lot easier, hasn't it?)
This is not to say that I always buy new books; I have a decided fondness for used book stores, and I am not shy about buying from http://www.abebooks.com/. I especially like the fact that this web site will keep a permanent search on for rare books and send you an email when they find them. Of course even Amazon sells used books now -- a welcome feature, to be sure.
I am not sure how to rate some books. They may be the best on their topic, but sightly tangential to my interests. Or they may be exactly what I want and need to read, but poorly organized and not all that well written. Does it matter if the binding of a book was so poor it started falling apart within 8 weeks of being printed?
Looking over my shelves, I am amazed at how many books I own that are reference books and seem inappropriate for listing. Does anyone really want to know what I think about The Handbook on Drug Abuse Prevention or The Dictionary of Film Quotations? I doubt it, and I left them out. Ditto for general reference books such as the Koran, The Letters of E.B White, and Breeding Zebra Finches. Finally, it seems that I read a fair number of books that are simply too obscure or limited in their print runs to actually be listed on Amazon and I am too lazy to type them in. In truth, a lot of the best stuff in some obscure sectors can best be described as "gray literature," and will never get wide circulation as a consequence. I am not too surprised that Full Revelations of a Professional Rat Catcher by Ike Williams (1889) is not an Amazon best seller, though I am rather shocked that William Vogt's Road to Survival is not listed; it was, after all, one of the largest-circulation and most influential environmental books of the 20th Century.