When we have many ebooks. searching for something inside our ebooks can be a problems.
( I plan to use it for searching my ebooks/ reference collection)

I try to search tools to help me, and the best I can found is dtSearch
https://www.dtsearch.com/PLF_Features_2.html

dtSearch can be Flexible and use Natural Language

I wish we can have something like Talk to Books but using our own collection
https://books.google.com/talktobooks/

Any opinion or better suggestion ?
Thank you