I keep a list on my desktop, in alphabetical order by author, of every book I read. I keep a separate list of nonfiction books. I assign 1-5 points to each book based on my enjoyment of it, and put DNR (do not read) next to books I started that weren't for me. Every other year I start a new list. Otherwise, I won't remember that I've read a book and will begin to re-read it. One benefit to this is that I can glance down the list every once in awhile and see whether authors I've enjoyed have a new book out.
I hate it when a book ends that I've really enjoyed. Usually I have a book I'm looking forward to waiting for me, but if I don't, I feel at loose ends until I start another really good book.
When books have lousy endings, I don't read any more by that author. I don't like it when a nice long book ties up all the loose ends, plus the conclusion, in a page or two. It's like the author rushed the ending by replacing it with a synopsis. Once, I read an engaging murder mystery, and in the end the victim had committed suicide. I didn't see that coming, and I was mad. It was a cheap trick.
What I really hate is when prolific authors start out writing good books, and at some point, every book is the same. It adds insult to injury when they continually repeat themselves in a book, an obvious ploy to pad a formulaic story.
Luckily, I never run out of good books to read.