I think mass market paperbacks in standardized sizes hold up pretty well considering everything. My collection mostly from the 1970s and 1980s held up pretty well up to 2010 but they are going yellow now because of the acid paper. Libraries rebind them and I notice they have a lot of rebound paperbacks of the same age that have the same yellowing mine have despite better storage conditions.
Some trade paperbacks are fine but because they're not really standardized quality is all over the place. I've bought some where the binding broke the minute I spread the book out. Hardcovers are more consistent than trade paperbacks but some still fail early.
Then there are just the accidents like the book I had in my backpack when I was outside in heavy rain but I think that was one book wrecked in about 300 circulations.