You've tried to ask Lucien for a book without specifying its name. Lucien's good, but he's not that good.

He could give you some hints, but his library is not one which encourages casual browsers. It's the sort where the librarian sits at a desk and you request a specific title and the librarian disappears into a back room for a time and comes back with a dusty tome in hand. In short, these are Closed Stacks, and Lucien will thank you to follow the rules.

Now go back to wherever you were.