Zoomi is for Hardcover only, or seems that way.

[fra...@bestweb.net]

One reason Zoomi is not often used is that there is no way to know if
a book is hard cover or not. It is a bit discouraging to spend time
finding something interesting only to find it is not a paperback. The
site should be spit into hard cover and paperbacks. If a hard cover is
wanted the local library will do fine.

[chris.thiessen]

Yes, that is a problem. I'm working on a way to show clearly whether
a book is hardcover or paperback, by showing a bit of the edge of the
book. Hopefully that will work well. If not, there's some other
things to try. Certainly a paperback version is a possibility, also.