The production values for this game are excellent; from the entertaining cut-scenes, level / character design and voice actors. It's a joy to play, and the various difficulty levels are spot on.
As the title suggests, this game takes place inside the grounds of an asylum, and as such the game map isn't exactly massive, although there is still plenty to explore.
It's a very linear game, although you may find yourself having to resort to the map several times inbetween objectives, which can become a little tiresome. Also, the batmobile and batplane both make an appearance, if only to remind you that you don't get the chance to pilot them (even the Amiga Batman game afforded you that opportunity).
While not as expansive and complex as GTA, it's a lot more satisfying in terms of pure combat and weaponry gadgets. It relies heavily on sub-tasks (I'd finished the game, while the counter claimed I had 40% left to play), but while it lasts, it's one of the most impressive games out there.