Greasy Fork is available in English.
Saves all available Preview pages from a Google Book as PNGs
< Обсуждения GBookDown - Download Google Books
There is a compatibility issue.
Try using an earlier version of Tor/Greasemonkey, Tor 5.5.2 and Greasemonkey 3.11 worked for me.
The script doesn't appear in Tor
I installed greasemonkey and the script, following the video tutorial. When I go to googlebooks and to the book I want to download, the script at the bottom of the page doesn't appear, therefore I can't start the download. Has anyone a solution to this issue?