Which Apple Ipad Ios?

[countrykid]

I have bought an Apple IPad mini 2 32Gb. I think this model is sometimes described as IPad mini with Retina Display. From looking at Apple's website, this model uses IOS8. To be honest I have no idea what the difference is between that system and IOS7 but presume the latter is somehow "better". I want to buy a book to help me to learn more about how to use it, and wonder if I need a book that refers to IOS8. How do I check that my particular IPad has IOS8? Thanks

[woofgang]

If its a mini, if you haven't got it now, the upgrade is free.

[Buenchico]

http://support.apple.com/en-gb/HT201685