Do you have a book? This is singular, you're asking if the person has one book. Do you have any books? This is plural, you're asking if the person has more than one book. Do you have some books? This is also plural, asking about more than one book. The difference between some and any is very small, and probably has to do with your expectation when you ask the question. When you ask with "any", it sounds like you're expecting the person to not have any books, or to have very few books. And you would be happy if the person had even only one. When you ask with "some" it sounds like you're expecting the person to have several, and probably won't be happy if he replies he only has one. It's usual, for example, to ask "Do you have any matches?" if you want to light a fire or a cigarette. You would be happy with only one match, and that's really all you want, but people usually carry around more than one match, so you ask the question in the plural. It's unusual to ask "Do you have some matches?" because it now sounds like you actually want more than one. If you ask "Would you like any coffee", it somehow doesn't sound as generous as "would you like some coffee". As if you're offering a smaller amount, somehow. I'm currently looking for bricks for my garden. It's much more natural for me to ask people "Do you have any bricks to give away?" because I'm not really expecting the person to answer positively. That is, not everyone has bricks. If I ask "Do you have some bricks to give away?" it sounds more like "Of course you have bricks, everyone has bricks, but I want to know if you have some to give away." So basically, any = expectation is few / some = expectation is many. That's why you have to say "I don't have any." not "*I don't have some." Like many things in language, the reality is probably much more subtle than I have explained here. But if you notice when people talk if they're using some or any, you'll get a feel for it.