Avoid old asylums at all costs. Really, what good ever came from them? Falling through the floor is the least one can hope for with one of these things.
I don't give books star ratings; I give them bite ratings. This is a bite. A book can get up to five of these evil-looking chompers, including half bites.
You can attribute your own wording to the ratings. Five's the best, three's decent, one and under isn't worth the gas to go to the library. I'll leave it to you to fill in the blanks.