Train journey from Granada to Barcelona

www.renfe.es is the "official" website for Spanish trains. However, I challenge you to find a less user friendly site. Truly, the philosophy of the train company is reflected in their site. You might have better luck just going to a travel agent or directly to the train station once in Spain for your tickets.
The train provides a very long ride. Unless you are deliberately looking to save the price of a night in a hotel, a low cost airplane will provide you with a better use of your time/money.

Thanks a lot.