Have you ever remembered reading something in one of your books, and maybe even remembered which book, but had no idea which of the couple hundred pages housed the beloved content? Don’t try the index or thumbing through the pages, simply go to books.google.com. There you can search within books to find where the content lies.
This works best when you have the book because many of the selections indexed by Google Books do not have full previews; however, the limited preview is more than enough to put you on the right page.
If your book is not available on Google Books, make sure you stop by amazon.com. Most books that have the small “look inside” logo over the cover image will provide a similar search to help you find what you are looking for.