
The fourth edition basic set shifts the majority of that material into the core rule books. Many source books published after the release of the compendiums required them for play. The previous edition of the GURPS rules consisted of a Basic Set as the core rule book, with GURPS Compendium I and GURPS Compendium II released later to collate alternative and advanced rules in a logical place. All the basic information needed to run a GURPS campaign is here with genre or world-specific information in other books. The second volume is titled Campaigns ( ISBN 978-1-55634-730-6) and addresses the information a GM needs to build a world. The first volume, Characters ( ISBN 1-55634-729-4), addresses what players need to know to create a GURPS character and play the game. The GURPS Basic Set for the fourth edition of GURPS was published in 2004 by Steve Jackson Games and contains the core rules for the fourth edition of GURPS. It was stated that "If you have an old Third Edition, and the new Compendium, you’ll have it all." Reviewers of the time called it "GURPS 3.5 edition" while Steve Jackson Game calls all their own non 4th edition GURPS material still in print "GURPS Classic". The third edition revised GURPS Basic Set replaced the adventure with an appendix covering rules added in supplements between 19 that were generic in application. The third edition GURPS Basic Set, released in 1988, combined all the books from the previous sets into one volume. Magic rules were omitted, but were released in GURPS Fantasy (1986). The original GURPS Basic Set included the combat rules from the previously published Man to Man. The Basic Set includes a "Characters" book (72 pages, covers character creation and development, skills, and basic equipment), "Adventuring" (80 pages, covers success rolls, combat, damage, running the game, game and campaign backgrounds, and animals), a 24-page book of charts and tables, and a 32-page book of two introductory scenarios, one a solo. The many additional supplements to the Basic Set enable GURPS characters to move easily from one gaming genre to another.

The character improvement system is skill-based.

The level of complexity used is completely up to the players. Basic combat is simple, but advance combat is very position-oriented, almost a complicated boardgame. GURPS stands for Generic Universal Role-Playing System – that is essentially a very flexible descendant of The Fantasy Trip.
