duplicate audiobooks

I have an iTunes account where I'm currently uploading all my Audiobooks. I have the whole series of Harry Potter and the Lord of the Rings, and my job involves driving children around to extra-curriculars, so they're very useful. I wanted to digitise instead of having to get the kid to change the discs all the time, so I'm uploading all my CDs to iTunes. The problem is, they upload in weird sections; e.g. I've just uploaded the first three discs of Lord of the Rings The Two Towers, and it's in fourteen sections, each registered as its own audiobook. I've checked; they're all registered with the same title, author, composer, artwork, etc., and they're all registered as compilations by different artists? Does anyone have any idea what's going on?