Pre-2018 book with non-linear story set in a hotel between 1920-1950

Title says basically everything I remember. There were a bunch of characters that kept circling back to this one hotel room. It's not a super long book, maybe between 200-300 pages? I think the title had a reference to the specific room number (like 35 or 34 or something?) It was also kind of a long title...

The cover had green/teal, red, and black with white/gold lettering.

I know it's not a lot of info, but would be grateful for any help!