In more depth, here’s how I think about stars and ratings:
One star means I’m sorry I read the stupid thing. Generally, I reserve this rating for books that I’m upset I wasted time on. There are only a handful of books that end up in this category. Examples include the Fifty Shades trilogy, Wuthering Heights, Alice in Wonderland, and Invisible Man. (That last one may change at some future date, when I don’t feel so bitter about my Comp exams.)
Two stars is like one star with a bonus. This rating is used for books I would never read again but there’s some reason I’m glad it’s been done. (Note the distinction between glad it’s been done and glad it’s over.) This is also the category I use for books that I think are too well written to be a complete waste of time but are entirely out of my zone of interest or enjoyment. Examples of books that fall into this category include Time Traveler’s Wife, the Twilight series (reading it all gives me carte blanche to hate without reservation), and The Great Gatsby.
Three stars is where my interest begins to perk up. These are what I might consider good books, though they often include books I’ll not return to. This is the essential “average” category: glad I read it; didn’t knock my socks off. Books in this category include Moby Dick, 1984, and Water for Elephants.
Simply, a four star book is a book I would probably read again OR I would read more books by the author, or more on the subject. Truth be told, I am a great re-reader of books so there are many examples on this list. Some, like Anna Karenina, Life of Pi, or Portrait of a Lady, are books I didn’t actually enjoy the first time around but would like to try again and see if I can’t make it work (this is what I consider an “itch” planted by a good writer). Others, like The Master or Rebecca, were both challenging and interesting.
Five star books, or Permanent Library Collection books, are those I would not only read, but also add to the precious real-estate that is my personal bookshelves. That is, these books are not only interesting and enjoyable, but they will probably be re-read more than once in my lifetime. They’ll also be loaned out.