single book, search results

The ISBN should refer to the actual book in question. ISBN-13 and ISBN-10 refer to the same exact item, but Web and Print do not. Given that this is coming from the web, I would say keep the Web ISBN. Also, ISBN-10 can be obtained from ISBN-13 if need be (vice versa as well), so let's just import that.

We don't have an official policy on this, but we should. This is especially problematic with WorldCat, where you get a gazillion ISBNs back (though there, we have no way to pick one over the other)