Click here to access a PDF file with a few helpful hints on upgrading to iOS 9.0. This doesn't go into any detail about the features of iOS 9, it just gives you the basic info you need to be aware of before you actually do the upgrade.
Take Control e-Book on iOS 9
There is a new e-Book available that you might want to take a look at. It is a crash course on iOS 9. Visit takecontrolbooks.com (click here) and use your MUG discount to get this e-Book with a 30% discount.
While you are there, notice that there is also a new e-book out on upgrading to El Capitan.
You might want to bookmark that link for future reference.