I'm afraid it is nothing like the first game.
It is better to view it as a stand-alone, bearing ties to the previous games in terms of lore. Personally, I did not really enjoy the changes they've made at first, but it is not a very bad game.
Character development works very different. No longer you are able to create a character freely; there is no character creation screen, but you are given a set of characters (four to be precise) with their own personality and their own class.
They do have a background story and react uniquely on certain events, but they are all bound to their own set of equipment.
One character, for instance, will always wield guns, but can switch freely between stances (in this case pistols or a rifle), offering some sense of variety in terms of gameplay and strategy.
You cannot, let's say, practice your combat magic to become better at it, but you will make key choices to steer your character into a direction you'd like to see. It offers some variety, but don't expect too much! There is certainly some replay value in this aspect of the game.
Certain things are kind of lacking, the dialogue and voices aren't top-notch, but this is not what Dungeon Siege is known for in the first place. They put effort into creating scenes where you are able to see the person you are talking to - however, their expression remains the same throughout the conversation. It is a little off-putting.
I'm also not fond of the inventory system and finding loot isn't always exciting.
Gameplay, overall, is entertaining, often casual, and boss fights can be very challenging. I'd suggest looking up a few videos about it to see if it's to your liking.
I enjoyed playing this game with a good friend but I haven't played it exhaustively. Just once 8D
If you expect a faithful sequel to the previous Dungeon Siege games, I'm afraid you'll be very disappointed.
I hope this answers some of your questions ^^