Our stay at the Library Hotel was a pleasant one. The reception staff was very attentive as was the staff on the second floor (the so called reading room, where the breakfast and the afternoon snacks are served). We had a Deluxe Room, which despite its name wasn't especially luxurious, but it provided a decent king-sized bed and was located on the 7th floor, which was nice enough (the hotel has 14 floors). Our hotel neighbours were slightly more active than we would have preferred (talking extensively in the corridor and going there and back all the time), but that is by no means the hotel's fault, and the sound isolation between the rooms is adequate. Our toilet got clogged without a specific reason, but the staff handled it very professionally, so no real problem there either. I would say that the hotel is worth its rather expensive price considering the location and the level of service.
The only minus I would like to mention is that it took 13 days (9 working days) for our 500 USD pre-authorisation to be cancelled from my credit card, a time period that I personally think is too long. The hotel couldn't do anything to speed things up even when I asked about it after 8 days of waiting for it to vanish. It usually doesn't take this long, so the hotel could try to update their practices on this (and there should be a possibility to cancel it manually when requested by the client, after the room has been checked).