MA,
I'm picturing walking up to the reference desk in my library, showing them the prescription from my doctor (or even just telling them about it) and them (being the reference librarian for that day), in turn, 'choosing' a book for me. If the prescription is for a particular book, that's just as strange.
It's not everyday that I'd want my librarian (of any standing) to know what my emotional bent is.
Makes me think of Google getting the settlement to put 'orphan' books online... and how far that could go... they'd have a way to monitor readers' choices.
My library doesn't currently keep a history of what its customers read (sometimes I wish they did, so I could have a personal printout for referrels and notes). I can see how a privacy infringement could arise if they did, tho, so I'm really thankful that they don't. I guess I'm throwing that element in while thinking about what you posted. But then, maybe I'm reading what you posted wrong. As I reread it, it still seems weird to me, and yes, curious, too.
... to add, most worthy of sharing here or anywhere - love your sharing!