It's a really broad field, so don't expect to get up to speed very quickly. A lot of people have recommended a lot of books already, and I could add to that list. One thing you might think about is Safari Books Online. You'll notice a lot of the recommended books are there, and even though it's a bit pricey, I think you'll find you'd save money by the time you get enough of the books that seem useful to you. You'll also loose nothing by jumping from book to book because they're too advanced/not advanced enough until you find one that's at your level.
I would recommend starting with one of the many OpenCV tutorial books, and maybe work your way through a few of those. Then move into books that cover more of the algorithms behind the library like "Multiple View Geometry" by Hartley and "Machine Vision" by Davies, among many others.
I would recommend starting with one of the many OpenCV tutorial books, and maybe work your way through a few of those. Then move into books that cover more of the algorithms behind the library like "Multiple View Geometry" by Hartley and "Machine Vision" by Davies, among many others.