Single most unique Turn-Based Strategy game around.
To begin with, there is the variety of the different kingdoms: Almekia, Esgares, Iscalio, Caerleon, Norgard, and Leonia. Beyond that you have the three difficulty settings. That alone gives a great deal of game play (for completionists). For good measure that is a staggering amount of hidden characters that you stumble upon by sending your officers out on quests.
There's more! Each officer recruits their own monsters to fight for them. Each one can, usually, class up upon hitting the required level. Some require certain items that you find on quests. Even the officers follow suit with classing up. Only they do so in such a way that if you don't do everything perfectly, you can't get the awesome class combinations (I could get in to the details of why,but that would drag this down more than I already have).
In the end I've spent hundreds of hours playing this game over and over and over. The only thing I wish it had was a harder difficulty: Once you've mastered the game, it's pretty easy. That's the only thing it is missing. It has a story, incredible soundtrack, compelling characters (save for certain ones), and a vast array of battalion combinations. It is sure to keep you playing for hours :D