What do the Hearts Mean?

Every once in a while, I like to remind my readers.  Here is my best attempt to explain what the hearts mean:

four-heartsLike it a lot or loved it; I recommend it; put it on your list!

three-heartsLike it; I recommend, with some reservations.

two-heartsI don’t recommend it, though it was compelling enough for me to finish reading.

one-heartI couldn’t get through it