For one thing, there is the notion that one should keep only things that thrill one ("spark joy") when touched. That would leave our house remarkably bare. It would not be more tidy, for we would have no dishes to eat from (unless they thrill my wife), and no brooms or other tools of cleaning. It would be dingy, eventually, for there would be no paint brushes or rollers. I suppose that we could rely on maid services, painters, and plumbers, but that sounds expensive. Probably I have missed a codicil that covers such dull items, but the book itself does not "spark joy" for me, which ought on its own terms excuse me from looking.
For another thing, she is for austerity in books. She believes that books not read as soon as acquired will not be read, and that books once read will not be reread. My experience says otherwise, for there are books that I have read the first time, with interest, twenty-five to thirty years after acquiring them; and there are quite a few books around the house that I do reread. Ms. Kondo thinks that in general people reread at most five books, and only scholars re-read as many as a hundred. This seems unlikely to me. Perhaps it is a matter of who hires her.
I found myself thinking of Hilaire Belloc's The Path to Rome, a passage making light of "real life":
... in these houses there is no honest dust. Not a bottle of good wine or bad; no prints inherited from one's uncle, and no children's books by Mrs Barbauld or Miss Edgeworth; no human disorder, nothing of that organic comfort which makes a man's house like a bear's fur for him. They have no debts, they do not read in bed, and they will have difficulty in saving their souls.I do wish Ms. Kondo and her soul all the best. But I don't plan to organize my house, and particularly my bookshelves, on her plan.