Not sure if it's the worst I've read or not, but American Pastoral comes to mind first. I'd heard only great things about it, and it's apparently even considered a "Great American Novel", but it was just absolute trash. Boring stupid plot, boring stupid characters (including cringe-inducing strawman characters), basically just spins its wheels forever before going nowhere. Also spent an obscene amount of pages talking about the process of making gloves, more than once, for no apparent reason. The entire book was just an absolute slog to get through. (And it's the most grating, boring kind of "first-world, upper-middle-class white male problems" story, like yeah wow boo hoo it must be so hard being so rich and successful, and having to deal with unrealistic strawman characters who are supposed to embody those mean leftists you don't like) (Like there was one character, I don't remember her name, but she tried to seduce the guy in one scene, and like I cannot get over what a ridiculous and unbelievable and unrealistic and over-the-top character she was, like it was so cringe-inducing) (It basically just felt like Atlas Shrugged, but with a more Literary slant, but also instead of making a bunch of long-winded philosophical monologues, the character just calls everybody stupid a lot)
There's a place for those who love their poetry
It's just across from the sign that says "Pros only"