How is a particular used book selling and how much is it around the world?

Over at BookFairs.Com, several book search engines are talked about, including viaLibri.

viaLibri, which has been recently redesigned, has an advanced search form that has many options.  It claims to be the world's largest search engine for old, rare & second-hand books, including searching international booksellers.

It's our go-to to get a sense of the market for scarcer material, especially when there's just too much "noise" on the individual marketplaces.

(https://www.bookfairs.com/book-search.html)