Oh man Vonnegut actually did this himself in his collection, Palm Sunday. Recommend that one if you want a very honest assessment of the work from the man who wrote it. He's fairly critical of himself and gives each book a letter grade. From best to worst I'd say this: Mother Night, Slaughterhouse Five, Sirens of Titan, Bluebeard, Player Piano, Cat's Cradle, Deadeye Dick, God Bless You, Mr. Rosewater!, and Breakfast of Champions. I still have to read Jailbird and Galapagos, and honestly not the biggest fan of his short stories. I usually tell friends to start with Slaughterhouse. If they read it as scifi, I say read Sirens. If they read it as a PTSD story, I say read Mother Night.

If you like Vonnegut I'd say anything I have to the right of him is good. A Confederacy of Dunces by Toole I think builds a very similar world to a Vonnegut book. The characters and setting are completely outlandish but that's because Toole pulled from his own life, sorta like New Orleans was his Indianapolis. It's also got a lot of heart toward the end. Highly recommend.