Is It OK To Give Up On A Book?

I love the Groucho Marx quote, “Outside of a dog, a book is man’s best friend. Inside of a dog, it’s too dark to read,” because I think it’s hilarious and it combines two of my favorite things, dogs and books. But I’ve had a nagging question about books for years; is it OK to give up on a book? And if so, at what point is it OK to give up on a book? This question of whether and when to give up on a book might seem trivial but for me it has both philosophical and practical implications.