What Makes A Book Great?
Before we start, I want to take a moment to emphasize that this is exploration not instruction. In other words, this look at great books, big G and small, is not me, expert, holding forth on the subject of greatness, but me, novice, exploring what might be necessary for greatness.
Okay, now that we got that out of the way:
The first qualities necessary for a great book (I shall use the small case when referring to both kinds) are the ones Peter Kreeft mentioned:
Which is another way of saying: a great book has to be a good book, as in a good story that catches our interest, holds together, and makes sense.
(Dang it! The rabbit just ate Sally Candleglow! Darn that fairy-eating rabbit!)