What is the best book in the Bible?
Well, that, of course, depends on how you define "best".
One way to try to determine it, though, would be to identify all the passages in the Bible that contain ideas that you consider good, and then compare the number of good passages found in each book of the Bible.
That's easy for me to do, since I have already marked as "good stuff" everything I can honestly call good in the Bible. Here are the Bible's books ranked according to the number of good passages.
So Proverbs, at 187, has the most good stuff.
But Proverbs is a fairly large book, with 31 chapters and 915 verses. How would it look if we adjusted the good stuff rankings to acount for the size of the book?
When we adjust for size, then, Ecclesiastes is by far the best book in the Bible (36.0 good passages / 100 verses).
(The overall average for the Bible is 1.5 good passages / 100 verses.)