There is
a forum thread dedicated to GetBooks, but it has been inactive for a few years and I don't see the plugin in
the Index of Calibre Plugins. The Calibre blog has
an article on GetBooks dated July 12th, 2020, but the article identifies the latest Calibre version as 0.8.21, which was certainly not the case in 2020. What is the status of the GetBooks plugin?