The story and characters are wonderful! It can get a bit tedious if you try for every ending, but once you complete the first one, the game lets you start from the halfway point and gives you some important extra story and interactions throughout the rest - and you keep your weapons, items and completed side quests from the first playthrough, as long as you start the next playthroughs with the same game file as your first.
There are a lot of optional sidequests which range from tedious to fun (for world building and character interaction between the main party). If you want to get all the endings, the only side quests you need to complete are the ones that give you weapons, as the last ending only becomes available to you once you collect them all - no need to do the other side quests, unless you want the reward money.
Combat is simple - hit the enemy til it's dead, or magic at the enemy til it's dead - the magic system in this game is pretty easy and satisfying to use, I probably beat more enemies using that than the weapons.
You don't get extra content or endings for higher difficulties, so feel free to play at whichever one you want - I went for easy cause I heard the game was particularly hard, but then ended up completing boss battles in like two minutes, before some of the dialogue was finished (the characters often have some good, unobtrusive conversations as you battle). I'm guessing the normal difficulty should be fine if you're a casual gamer like me.