From the Space Quest FAQ:
This is an official novelization/hint book for Space Quests 1-4 in the First Edition, and 1-5 in the Second Edition.
- The Official Guide To Roger Wilco's Space Adventures, by Jill Champion & Richard C. Leinecker
This is an official novelization/hint guide for Space Quests 1-5. There are two editions. The first edition portrays SQ1 from the perspective of the original version of the game (and only goes up to the 4th game), and the second from the perspective of the remake.
- The Adventures of Roger Wilco: The Sarien Encounter - Malibu Graphics
This is a comic book series, published by Malibu Graphics years back. Apparently, they only made three issues. The print run was very small, so these are almost impossible to find. It loosely follows the plot of Space Quest I.
Behind the scenes
If you are interested in stories written by the fans, see Fan Fiction.