I thought Farewell to Arms was boring. For Whom the Bell Tolls was great. I think the difference is the romance was more at the forefront with the former, and with Hemingway being so matter-of-fact, it didn’t work. But for a war story about a bridge, that style worked great.
Gulliver’s Travels is much funnier if you’ve read Robinson Crusoe first. It’s a parody of it.