Four of the objects of constant width; a revolved Reuleaux triangle, pentagon, heptagon and a Spheroform with tetrahedral symmetry.

When placed under a book and rolled they will keep the book at the same height, and each object will only have two points of contact like a sphere.

I printed each shape in two halfs and glued them together with a peg, but I have also included the complete shapes in the STL files.

STL 3-is the revolved Reuleaux triangle

STL 5-is the revolved Reuleaux pentagon

STL 7-is the revolved Reuleaux heptagon

STL Spheroform-is the Spheroform with tetrahedral symmetry

Checkout some of the youtube videos people have made about them:

https://www.youtube.com/watch?v=cUCSSJwO3GU

https://www.youtube.com/watch?v=fOojOfpcPZM&t=28s

Infomation about the Spheroform with tetrahedral symmetry:

http://www.xtalgrafix.com/Spheroform2.htm

These are not my idea, but I just wanted to have a go at modeling and printing them for myself. Hope you enjoy them as much as I do!