Johnson authored or co-authored several books for Steve Jackson Games. One of these books, GURPS Monsters, won a rating of A in a review published in Games Unplugged. John G. Snyder of gamingreport.com rated the book at 4 1/2 stars, saying, "You will be pleasantly surprised and not a little disturbed." Freelance Writer Craig Oxbrow says in a 2001 review of the book for rpg.net, "GURPS Monsters is a wealth of ideas and inspiration for monsters as characters," and that it "will see use beyond the GURPS system." Kenneth Hite from Out of the Box reviewed Johnson's book GURPS Japan: beauty, terror, and adventure, 2nd ed. in 1999, concluding that "medieval Japan, broadly defined, is suddenly one of the most solidly playable milieux in Gaming."