It would really help if we could sort "By Book" results by the number of hits. Often I'll run a search and there'll be dozens of books with 1 or 2 hits, then a couple hidden away in the middle with several dozen hits. It's clearly those resources I want to be looking at.
They don't always appear in ranked search, because if those hits are spread out over many articles within the resource, the individual articles won't rank highly in a ranked search.