"A page is a Door" by Remy Charlip

"A book is a series of pages held together at one edge, and these pages can be moved on their hinges like a swinging door. They could also be half-doors, doors with windows, double doors, like fold-outs, doors with attachments, pop-ups, textures or moving parts, and shaped doors.

Of course if a door has something completely different behind it, it is much more exciting. The element of delight and surprise is helped by the physical power we feel in our own hands when we move that page or door to reveal a change in everything that has gone before, in time, place, or character.

A thrilling picture book not only makes beautiful single images or sequential images, but also allows us to become aware of a book's unique physical structure, by bringing our attention, once again, to that momentous moment: the turning of the page."

quoted from "A Page is a Door"
by Remy Charlip

What a great analogy by Remy Charlip: the page turn as the reveal brought on by the active reader, eager to know what comes next.