Perhaps my favorite type of reading, is where the genre's of humor and science fiction intersect (think Venn diagram).
I literally tracked a book for more than two decades before finding it, as it is my favorite funny SF collection. This was back before the internet. Now I have at least five copies of the book, just in case...
So, if you want a laugh out loud experience, try these some time...
Bill, the galactic hero (Harry Harrison). Young Bill (oh, excuse me, Bil. As a sergeant tells him, "Bil. Two L's are for officers only, learn your place.") enlists for some space fighting, becomes a hero, criminal, G-man (G = garbage in this case), revolutionary, double agent, spy, convict, and sees the universe.
Robots have no tails. (Henry Kuttner) The book that took me decades to find. Inventor can only invent things when drunk, then has the resultant problems when sober trying to figure out what he invented.
The Witches of Karres (James H. Schmitz) Space captain rescues 3 witches (girls with a variety of psychic powers) , and shenanigans ensue.
The Stainless Steel Rat/The Stainless Steel Rat's Revenge/The Stainless Steel Rat Saves the World (Harry Harrison). In a galaxy where crime no longer exists, to be a criminal is a funny business.
Another fine Myth (Robert Lynn Asprin) Pun filled fantasy.
Retief stories and books (Keith Laumer) Diplomacy of the future, where hero Retief is saving his venal superiors from themselves. About 50 stories and at least 3 books.
A Night in the lonesome October (Roger Zelzany). A faithful Dog helps his master keep the old ones from reclaiming the earth. Countdown of days in October to the ceremony.
Space for Hire (William F. Nolan). Better known for Logan's Run, this one features a mix of hard-boiled detective Sam Space trying to save the solar system and make it with beautiful dames, including a three headed Venus chick.
Redshirts (John Skalzi). Hugo winning novel about the dangerous of going on "away missions" with the heroic captain and science officer, and why the death rate for redshirts is so astoundingly high.
I know, I didn't include Adams or Pratchett, so sue me...
Honerable mention for various short stories: Frederick Brown, Robert Sheckley.
Ya'all feel free to add to my list...