This one is just as good or better than it's predecessor in every way except it's technical aspects and maybe the story.

There's more non-lethal options.
There are multiple characters to play as, with different spells and dialogue.
There's a greater variety of spells and perks to choose from.
You can customize your difficulty: footstep noise, enemy perception, health regen, damage and much more.

Even though the first ones replayability was high, with the addition of new game+, custom difficulty, even more spells to choose from and craftable bonecharms that stack up to 4 times, D2s replayability surpasses the original.
A single playthrough of D2 took me significantly longer than D1 while trying to explore the levels as much as i can (although that might be different for others).

There are two levels which are really innovative and stand out from anything i've seen before, one of those you can see in the trailer of the game a house which can rearrange it's walls and change it's layout at a press of a button, and the second one lets you explore the same level in two time periods, letting you phase between the two at your will.

The main negative i have with this one is the story, more specifically the villains, which you basically meet for the first time and dispose of during the same level, so there's little incentive for you to care about them at all, yes there are story bits scattered around in the logs/books that flesh them out but still. Compared to D1 where most villains you meet and get to know between every mission, in the pub D2 feels worse.
The outsider feels different, in a bad way, they've changed the voice actor so it's probably that, but he just feels completely different compared to the first game and doesn't convey the same emotions.

And of course, the technical problems, having played this 2 years after release, it wasn't as bad as for some others in the past but still, the game crashed twice.
The main technical problem for me is that the sound would randomly cut out/muffle in some instances. I'd listen to a guard conversation and just rotating the camera or slight movements would completely muffle the sound. Same would happen when my character would talk. It might not seem like much, but when it happens multiple times every minute it can get quite annoying. To me this was a major drawback from enjoying the game for the first few hours until i got used to it. It's a widely known bug but even 2 years after release it still hasn't been fixed.

Apart from those negatives, there's not much reason not to try this one especially if you're a fan of the original.

This one is just as good or better than it's predecessor in every way except it's technical aspects and maybe the story. There's more non-lethal options. There are multiple characters to play as, with different spells and dialogue. There's a greater variety of spells and perks to choose from. You can customize your difficulty: footstep noise, enemy perception, health regen, damage and much more. Even though the first ones replayability was high, with the addition of new game+, custom difficulty, even more spells to choose from and craftable bonecharms that stack up to 4 times, D2s replayability surpasses the original. A single playthrough of D2 took me significantly longer than D1 while trying to explore the levels as much as i can (although that might be different for others). There are two levels which are really innovative and stand out from anything i've seen before, one of those you can see in the trailer of the game [spoiler]a house which can rearrange it's walls and change it's layout at a press of a button[/spoiler], and the second one lets you [spoiler]explore the same level in two time periods, letting you phase between the two at your will.[/spoiler] The main negative i have with this one is the story, more specifically the villains, which you basically meet for the first time and dispose of during the same level, so there's little incentive for you to care about them at all, yes there are story bits scattered around in the logs/books that flesh them out but still. Compared to D1 where [spoiler] most villains you meet and get to know between every mission, in the pub[/spoiler] D2 feels worse. The outsider feels different, in a bad way, they've changed the voice actor so it's probably that, but he just feels completely different compared to the first game and doesn't convey the same emotions. And of course, the technical problems, having played this 2 years after release, it wasn't as bad as for some others in the past but still, the game crashed twice. The main technical problem for me is that the sound would randomly cut out/muffle in some instances. I'd listen to a guard conversation and just rotating the camera or slight movements would completely muffle the sound. Same would happen when my character would talk. It might not seem like much, but when it happens multiple times every minute it can get quite annoying. To me this was a major drawback from enjoying the game for the first few hours until i got used to it. It's a widely known bug but even 2 years after release it still hasn't been fixed. Apart from those negatives, there's not much reason not to try this one especially if you're a fan of the original.