One of our buildings has a space designated as "the library" with (as I recall) mostly standard study carrells that are pretty much as you describe. No fixed desks or reservations. You just find a space to read or work on your laptop. I'm not in that building very often but it's always seemed pretty quiet to me. Though to be honest when I've traveled there I often just worked out of the cafeteria because pre-pandemic I'd often run into people I knew.

ADDED: One practice which probably makes sense is to physically separate a quiet reading room from other areas. That way people aren't wandering by and having conversations.