Any recommendations on books I should get? It does seem smart to develop for a growing market as opposed to an oversaturated one.
In my opinion, Windows 8 RT is the best path for you. It is empty right now but it is growing.
For other platforms: For Android, I'd recommend youtube honestly. There are plenty of great websites that will teach you the basics quick (you will have to learn Java though if you don't know it). For iOS, iOS 7 cookbook is good I'm assuming ( I have the 6). Both are heavily saturated though. If you have a background in C, doing Android Operating system stuff can be good.
For Windows 8 Apps, just follow Microsoft's examples online. No need for books. You can develop in C++ and use things you already said you know. It won't be that big of a leap for you, only in learning the new API. If you know someone with an .edu adress, sign up for Dreamspark and they will waive any license fees and you can download all the necessary software for free (including Visual Studio 2013 Professional).