Prompted by a note hidden beneath a flap, Molly finds herself first in a world (with, significantly, a white rabbit) where select insides and outsides are inverted. Subsequent flaps see her finding and passing through further concealed doorways into an M.C. Escher-style "impossible staircase," a maze with tessellated shapes, a set of infinitely receding hallways, and six more "implausible but not impossible" settings that likewise demonstrate some of math's central tools and ideas--often in an interactive way that requires folding, recognizing patterns, or interlacing pre-cut elements. Artymowska fills her big, square illustrations with both clearly drawn examples of each main concept and smaller details to search out, such as sets of nesting dolls to match up. --Kirkus Reviews (starred review).