This book is small, squarish with a brushed metal effect silver cover.
It is the first book in the sequence, and if you were to buy just the one, then this is the one that I would recommend. There is a decent amount of thoughtful text, but not so much as to detract from the photos, which are really why most folk buy these books.
Projects include a giant beach ball you can roll down a hillside in, a 'hairy building' of protruding wooden staves, and a spider like room designed to perch within a crevice.
As the author points out, these buildings are not that far removed from earlier follies, but they exist to make us think and question.
Some reviewers have complained about duplication, I suspect that there are/were two imprints, one by Universe and one by Thames and Hudson. The three that I have bought are this book,XS Extreme: Big Ideas, Small BuildingsXS Green: Big Ideas, Small Buildings
Although a few architects and projects recur, there is enough new in each book to make it worthwhile.
If you have deep pockets you might also enjoySpaceCraft: Fleeting Architecture and Hideouts