From the Introduction:
This book contains an abbreviated version of the basic To Challenge Tomorrow rules plus specific adaptations and powers for use with CHALLENGERS, the superhero adventure background for use with TCT.
TO CHALLENGE TOMORROW is a simple, general system, and with these rules and the specific material provided you have everything you need for unusually flexible comic book-adventuring set in the near future background described in book #2, or in a background of your own design. The second book of this set contains background and adventures for use with this system, or for adaptation to other systems.
Challengers is a skill-based game with a strong emphasis on role-playing and imagination, adding depth to the background and character development, realizing the as yet unanswered promise of superhero gaming.