I'm alright with a few curses in a book since that isn't too bad and D'Arvit is fine since its from a language I don't understand but I've seen authors use the F/A/D/B/S/R Words 40+ times in a book and its like not cool dude, You take away from the story.
In order to demonstrate my point, I will first discuss what a word is and why it is used in the context of writing. Words, In the case of books, Are written or printed characters or a combination of characters representing a spoken word. Words are meant to convey meaning from one person to another. That meaning the words create is the most important part of a book, And it is also why curse words should not be used in books.
Unlike other words, Curse words do not register with a set meaning. When people hear the word bitch they are not thinking about a female dog they are thinking about the fact that someone just insulted another.
For this reason, Curse words do not belong in books because they are empty words which can and should be replaced by words with actual meaning.