Bake brownies according to package directions in a 9x13-inch pan; let cool completely. Spread with chocolate frosting and cut into 12 rectangles.
Cut gummy worms into pieces and press into the top and sides of brownie.
Microwave Tootsie Rolls for 3 seconds on high. Roll each into a 1/2x3-inch strip. Cut with scissors to straighten; repeat with the remaining Tootsie Rolls. Place strip on brownie to make the binding. With vanilla tube frosting, pipe horizontal lines to resemble the pages of a book. Pipe two white dots on the gummy worms head and add mini chocolate chips as the eyes.