Marvel Super Hero Adventure Gamebooks #5
From the back cover:
A deadly disease threatens the Fantastic Four! You must find the cure before it's too late!
You are the ever-lovin' blue-eyed Thing, rocky orange member of the Fantastic Four, plagued by a deadly enemy you cannot defeat with your monster strength alone.
MARVEL SUPER HEROES Adventure Gamebooks are based on TSR, Inc.'s popular MARVEL SUPER HEROES role-playing game, but you needn't know the game to enjoy the exciting adventure in this book. All you need to do is get one standard, six-sided die (not included), ready your huge rocky fists and indefatigable will, and assume the role of the Thing as he seeks to save himself and his teammates from a deadly disease in ONE THING AFTER ANOTHER.