Cannery Row by John Steinbeck. A simple, feel good story with some fantastic characters and great insights into the human condition. I’ve re-read it at least 4 times now and always experience that wide eyed wonder you get when you know you’ve learnt something special. Has a sequel as well, Sweet Thursday, which is equally inspiring.
Mind you, I am a huge Steinbeck fan, slowly working my way through all of his books. My favourite is East of Eden, but that has a fair amount of unhappy material so doesn’t really fit your criteria. I would urge anyone to read it though, amazing book.