GURPS Fourth Edition is a 21-book series with 21 released primary works first released in 2002 with contributions by William H. Stoddard, Peter Dell'Orto, Dan Howard, Matt Riggsby, Phil Masters, Steve Jackson, S. John Ross, Daniel U. Thibault, Michael Suileabhain-Wilson, Sean Punch, David L. Pulver, Kenneth Hite, John M. Ford, Jonathan Woodward, David Morgan-Mar, Jon F. Zeigler, James L. Cambias, Kenneth Peters, Shawn Fisher, Michael Hurst, Hans-Christian Vortisch, Jake Steinmann, and Jason "PK" Levine.