The destruction of books leads to happiness in two major ways.
First, by destroying the books, you end the sort of inequality of intellect that you used to have. You stop having the smart people that everyone hates and the mass of "dumb" people who don't care about or understand the books. With no books, you don't have this elite who understands them.
Second, you stop having people who are insulted by the books. Beatty mentions black people and Mormons, for example. If you do not have books, you do not have anything that will say things that annoy these various groups. It is sort of like the idea of political correctness today -- you try not to annoy anyone.
