Need Recommendations] A book with an unlikeable protagonist who is not in gainful employment, a slob if you will, and whose potential has fizzled out, like a failed gifted child, and is not particularly sad on the surface.

The closest I can think of is Chip from Franzen’s The Corrections. Not someone who feels a lot like Holden Caulfield or wishes to do better (at least in the beginning). Adjectives include manchild, failure, drunk (and other substances), self-aggrandising, cynical, snobbish, and so on. Thank you!