My mother must read every book she starts. Often she complains about a book ad finitum. I tell her life is to short, just read something else, but she is compelled to finish them.
The person in question hated 64 out of 172 books, about 30%, which doesn't seem outrageous if she is adventurous in her reading. Higher than me as 90% of my reading is stuff I know I will like.
Too many books, too little time.