I think their skill lies in being able to filter the entire library's contents down to a handful of best guesses. If you ask them "give me all the books whose main topic is compilers", you might have too large of a result set, and maybe they would prompt you for a more specialized keyword that they can use to further narrow down the results.
I suppose it is better than brute-forcing an entire shelf of books :)
I suppose it is better than brute-forcing an entire shelf of books :)