Because that would be sufficiently transformative, and passes all the fair use tests with flying colors.
If you cut up the book into paragraphs, sentences, and phrases, and rearranged them to make and sell your own books, then you are likely to fail each of the four tests.
But even if you manage to cut those pieces up so fine that you can’t necessarily tell where they come from in the source material, there is enough contained in the output that it is clearly drawing directly on source material.
There are dozens, depending on what exactly you want to do.