The Xplosiv edition of Dungeon Siege : Legends of Aranna is available on
Amazon. This is the version that I have and it is a standalone copy (i.e. it has the original game as well so you don't need to get that to run it. I actually have the original separately as it happens) Not sure if that is the case for all editions so be sure to check.
Only played the opening but I have to admit that I'm impressed at how much it still feels like an Ultima game, even in the Dungeon Siege engine. There is a reference to the events of Ultima 5 (which I played way back when on the Commodore 64. Yes, I'm THAT old
) so a bit of background reading might be helpful.
For anyone that is unsure, I think the resemblance to the old Ultima games is a good thing. There are reasons why these games are classics.