Pop-up books can range from quite simple to very complex. Many use an accordion fold structure as a base with cut-outs in the sheets or with extra elements attached to those sheets. 

Image: Rein Jansma, Stairs

Tunnel books create a window-like or diorama effect. They can be made using a box in which cut sheets of paper are inserted or the sheets can be mounted onto two accordion fold structures.

Image: Michelle Ray, God Created the Sea and Painted It Blue So We Would Feel Good on It

Cut out pages can also be arranged radially around a central axis, creating a carousel or 360 book. In this example, a mouse has gotten into a Swiss cheese and is having a field day!

Image: Yusuke Oono, In a Cheese