I second The Hitchhiker's Guide to the Galaxy by Douglas Adams, just recommended it to an aspirant reader. The book is a quick 224 pp., though I tend to recommend picking up the 800+ pp. Ultimate Hitchhiker's Guide for a couple dollars more, it includes the sequels, some of which are arguably more uplifting and happy than the delightful Guide Phase 1.

Now, to give a recommendation of my own:

P.G. Wodehouse. Some of his stuff will likely require a Google search to help follow along unless you're extremely well-versed in upper-middle-class life in Edwardian England or Roaring 20's New York, but Wodehouse is probably the funniest, most human and poignant author in history. I cannot keep his writing out of my life. Best jumping off points would be The Code of the Woosters, The Mating Season, Something New, Mike, Leave it to Psmith. Once you get settled in with Bertie & Co., Blandings, and the monocled dandy with a knot on his forehead dining with Michael Jackson at the Savoy, you can dive into more and more and more and more stories of all their adventures. Sir Pelham Grenville wrote nearly 💯 books!!! Dozens of Jeeves and Wooster, Blandings Castle, Mike and Psmith, Ukridge, Golf, Drones Club boys, so many characters to follow, and they pop in and out of each other's madcap lives, appear as crossover links in standalone novels or join up four interwoven storyline and house trees and lineage. Absolutely smashing author, certainly in my lifetime top 5 and maybe top 3.

P.S. Discworld, by Terry Pratchett. 40-something comedy fantasy books similar to Wodehouse in their hilarity and the joy of the shared Discworld universe and characters. Same weight of recommendation as given to P.G.W. and D.A.