can I return a book? never opened, within hours of purchase (wrong book of series)

Anything that you've bought, including books, will show on the account's purchase history.

If by 'get the book' you mean download it then go to the Purchased tab in the iBooks app on your iOS device, or iBooks app if using a Mac (you can also redownload it via the Purchased section in a computer's iTunes, assuming that it's still in the store and you haven't moved countries. If it doesn't show check : Hide and unhide iTunes Store, App Store, or iBooks Store purchases - Apple Support

Try the 'report a problem' link from your purchase history : log into your account on your computer's iTunes via Store > View My Account (Store > View My Apple ID on iTunes 11) and you should then see a Purchase History section with a 'see all' link to the right of it ; click on that and you should see a list of your purchases ; find that book, click the arrow to the left of it, click the 'Report a Problem' button :

and then the 'Report a Problem' link on its line :

and select 'inadvertently purchased' as the problem and fill in the details (iTunes support should reply within, I think, about 24 hours).

In my purchases, the only thing that shows up is app purchases. Where do I get to the book?