To extract text from photos and non OCR-ed PDFs Tesseract[1] with language specific model[2] never fails me.
I use my shell utility[3] to automate the workflow with ImageMagick and Tesseract, with intermediate step using monochrome TIFFs. Extracting each page into separate text file allows to ag/grep a phrase and then find it easily back in the original PDF.
Having greppable libraries of books on various domains and not having to crawl through the web search each time is very useful and time-saving.
[1] https://tesseract-ocr.github.io/