Ok, this is excellent. I have nothing to correct here. 

If you want the true books (printed ones) I think you should go to the book shops and try to find some of them. 

If there's any kind of book fair in the USA, just like there's in Serbia, you can also buy some Spanish books. 

However, if you prefer e-books in PDF, actually you don't have to buy them, you can just download them. 

I hope this helps :)

If you have any further questions, feel free to ask me. 

Have a nice day.