That's why hpmor was only 660000 words?

If you think you can point to an unnecessary sentence within it, go ahead and try. Having a long story isn't the same fundamental kind of issue as having an extra sentence.

How about the second sentence^1^?

Every inch of wall space is covered by a bookcase. Each bookcase has six shelves, going almost to the ceiling. Some bookshelves are stacked to the brim with hardback books: science, maths, history, and everything else. Other shelves have two layers of paperback science fiction, with the back layer of books propped up on old tissue boxes or lengths of wood, so that you can see the back layer of books above the books in front. And it still isn't enough. Books are overflowing onto the tables and the sofas and making little heaps under the windows.

Each bookcase has six shelves, going almost to the ceiling.

The exact number of shelves is superfluous for the point being made, as is specifying that the bookshelves almost go to the ceiling. We get it, there's a lot of books. Enough books to contain even the longest Yud tweets.

[1]: Excluding a full page long spiel of self-promotion, metatext and a paragraph of what I assume is supposed to be foreshadowing for spooky things to come.