Okay, this won't be as easy. There are only three books in the bible that have more good stuff than bad (Ecclesiastes, Proverbs, and James), so the best book had to be one of them. Ecclesiastes won that contest hands down.
But what about the other 63 books in the Bible? Well, let's start with a scatterplot of the net good by the number of verses in each of the Bible's books.
There are three books that fall well below the line: Revelation, Deuteronomy, and Jeremiah. But which of these is the worst?
It might help to separate the Old and New Testaments.
And here's a plot of the netgood by number of verses in the New Testament books.
So at least we know the worst book in the New Testament. Revelation.
Now back to the Old Testament.
There they are again: Deuteronomy and Jeremiah. But it's hard to tell from the graph which is worse.
It might help to look at the net bad on a percentage basis. How many net bad verses are there in 100 verses? Here's a plot for just the three worst books.
So it looks like Revelation wins the prize.
[I should mention, though, that there are a few small Old Testament books that have even higher percent net bads. Zephaniah, Obadiah, and Amos have net bad percents of 54.7, 42.9, and 40.4, respectively. (These three were the low outliers in the last plot of the previous post.) But they are much smaller than the big three bad books -- Revelation, Deuteronomy, and Jeremiah.]