Out of This World Jokes about the Solar System: Laugh and Learn about Science (2012) by Melissa Stewart and Gerald Kelley
Astronuts: Space Jokes and Riddles (1991) by Charles Keller (author) and Art Cumings (illustrator). Out of print.
Jokes and Cartoons from Outer Space: For Young Aliens Ages 7-11 (2006) by Joel Rothman
Outer Space Jokes: Wacky Words (1993) by Greg Lee
The Intergalactic Joke Book (1989) by Ann Droid Guaranteed to give you atomic ache. Probably out of print but used copies available.
Intergalactic!: 150 Cosmic Jokes about Space! (2009) by Amanda Li (Author), Martin Chatterton (Illustrator)
Galaxy's Greatest Giggles (2008) Matt Rissinger and Philip Yates (Authors), Ethan Long (Illustrator)
The Intergalactic Joke Book (1989) by Ann Droid Guaranteed to give you atomic ache. Out of print but used copies available.
Space Jokes (Hal-Larious Joke Books) by Pam Rosenberg (Author), Mernie Gallagher-Cole (Illustrator) 2010
Astro-Nuts!: Riddles about Astronauts and the Planets They Love by Rich Walton and Pat Bagley (1995)
More Children's Books
Smarties Guide to the Galaxy by Michael Powell (2002) How to stay cool and survive in space.
Totally Gobsmaking Galaxy (2009) by Kjartan Poskitt Check out his homepage.
Astrosaurs series by Steve Cole
"Captain Teggs is no ordinary dinosaur - he's an astrosaur! On the incredible spaceship DSS Sauropod, along with his faithful crew, Gypsy, Arx and Iggy, Teggs rights wrongs, fights evil... and eats a lot of grass." (quote from his fun website).
Cows in Action 11 - First Cows on the Moon by Steve Cole
Aliens Are Coming! by Meghan McCarthy (2009)
The True Account Of The 1938 War Of The Worlds Radio Broadcast. Click here for her website.
Here Come the Aliens! (1997) by Colin McNaughton
Aliens Are Coming (2008) by Colin McNaughton
"They come from planets near and far some big, some small, some quite bizarre."
We're Off to Look for Aliens (2009) by Colin McNaughton