...Was, for me, a single small room in the village, with stacks only around three walls, and not full height or complete at the back - yet it seemed full of discoveries once I had 'graduated' to the adult sections (aged 14). Furthermore, merely for the trouble of filling-in a card, I could order... anything! from inter-library loans.
The next step-up was the Bristol City Library, which was essentially endless - the problem being to decide which of the inexhaustible riches, I should borrow on this particular day... The only problem being a two hour round trip to get there and back.
(It was only seven miles away, but the buses were very infrequent, unpredictable, and slow...)
Probably no other library since has been qualitatively a step-up for me; all university libraries being experienced as variations on the Bristol library... but they have often been superior as places to read, study, and have a coffee.
I have a similar love for second-hand bookshops (not so much for new bookshops) - but good libraries have the great advantage of a higher number of worthwhile books, and a higher ratio of worthwhile to worthless ones.
Of course beautiful libraries have an extra dimension - although the beauty of a library is a different thing from architectural beauty - it is more a matter of niches, than of overall effect.
My current favourite is the Literary and Philosophical library in Newcastle (above) - which is a pleasing early 19th century building, and well provided with various niches. A good place for treading-water among the stacks, and fishing for (or being hooked-by) who knows what...*
Where it all began... Thanks to the legendary 'Mrs Everson', Librarian