I was considering getting the Ultimania books for my three favorite games in the series (VI, VII, X) but when I started browsing from them at Amazon, I noticed that some of the games have different books. I can see Ultimania, Ultimania Omega, Battle Ultimania and Scenario Ultimania. What's the exact difference between each. I planned on getting three books but now I can't decide. I thought there was only one for each game¿