It would be nice to have an interface to calibre search of your ebook metadata. This can be done by wrapping calibredb.
Example use case. Run M-x calibre-search , prompt appears type title:space tags:scifi search is populated with the titles and metadata of matching books and you type to narrow hit enter book opens.
Also open-last-book and open-recent-books. I could probably add this to my existing wrapper.
My solution to this has been to export the library as a bibtex file, which is a built in feature of Calibre, and then use ivy-bibtex (could just as easily use helm-bibtex) to search the library. You need to make sure the file path is part of your bibtex export, but this is easily done. Also make sure you export tags.
https://github.com/davatorium/rofi
Presumably would be about as easy to do in elisp.
A call to calibredb in a library of thousands of books on ssd is only 1/3 -> 1/2 a second