Here's a GT review of the PSP version, if you want to get an idea of what it's like. Probably minor spoilers and stuff, so just check out the beginning or parts of it quickly to get the gist of the gameplay.
It's sorta a little like Advance Wars I guess in the sense it is turn-based. Not too much though, no recruiting mid-battle, you have to use the forces you start the battle with to win it through the end. No splash screens of units fighting, everything is kept on the main screen. It's obviously got a fantasy theme to it, the art style is great and the story is interesting, very over-the-top politics, with plenty of high stakes to keep things interesting.
There's a main map with checkpoints, where you can start battles, which take place on a separate screen. There's a very strong RPG element, with lots of items to buy at the towns on the main map. You have classes to level, jobs to assign your members, skills, and so forth, all which allow for some really diverse strategies to use in battle. I always like to think of the genre as an unbalanced chess game on a 50x50 board, with much more interesting set pieces.
It's definitely a commitment, a good 50-100 hours depending on how much you want to complete (lots of sidequests and optional battles). If you enjoy the genre though, the time spent plotting and playing the battles flies by!
