One of the few novels from the existential period, that I am glad to have read would be Thomas Mann’s The Magic Mountain.
It describes a young German engineer, who goes to visit a cousin in a TB sanatorium located in the mountains of Davos, Switzerland. It’s certainly morbid, but it was also an example of good storytelling.
I have tried to ‘pierce’ or chisel my way into a few other books by Thomas Mann, but I never found another of his books quite as approachable as this one.