8 books in series

The X-Files

The X-Files is a 8-book series with 8 released primary works first released in 1994 with contributions by Charles L. Grant, Kevin J. Anderson, Chris Carter, Ben Mezrich, Elizabeth Hand, Chris Carter, and Max Allan Collins.

The X-Files: Goblins
Whirlwind
The X-Files
Ruins
Antibodies
Skin
The X-Files: Fight the Future
The X-Files: I Want to Believe