Off topic: I understand your arguments, but every time I read something like "mostly cheap used hardcover", as an author myself I have to ask: You are aware that the creative behind the work you read does not get a dime from you?
Which isn't to say used-book sales should be illegal, but that if you can afford it, why not support the person behind the ideas you're profiting from?
Not according to the law, you aren't.
Also, there are plenty of ideas involved in building cars and houses. They're not just random piles of wood, metal, and plastic, any more than a book is just ink smeared on paper.