The Big Time, Fritz Leiber
I picked this up at the same time as The Wanderer, another Leiber Hugo winner. The disappointment I had with The Wanderer didn’t dissuade me from diving in to this one, which is a good thing, because The Big Time was a very enjoyable book.
The setting is a bubble in time known as “The Place” where warriors in a cross-time “Change War” between anonymous factions known only as “Snakes” and “Spiders” go for recuperation after their battles. The viewpoint character and first-person narrator is Greta, an entertainer (with more than just song and dance implied by the title) attached to The Place. The conflict comes when somebody in The Place makes off with the machine that opens and closes the doors back to real time.
The resulting locked-room mystery isn’t more than an average sf story puzzle; what makes the story jump is the way the narration shows both that Greta sees real importance in her work at The Place, and the “Change War” going on outside the doors, and yet she can still be cynical about her role in the war, and the motives of the soldiers and Spider leadership.