6 books in series

The Hitchhiker's Guide to the Galaxy

The Hitchhiker's Guide to the Galaxy is a 7-book series with 6 released primary works first released in 1979 with contributions by Douglas Adams and Eoin Colfer.

The Hitchhiker's Guide to the Galaxy
The Restaurant at the End of the Universe
Life, the Universe and Everything
So Long, and Thanks for All the Fish
Young Zaphod Plays It Safe
Mostly Harmless
And Another Thing...