Although there is more puzzle variety and a new enemy type and weapon, the story took a very weird turn near the end, which should be in the base game.
The story also isn't that interesting anymore and the final boss battle is atrocious, it glitched for me like 3/4 times. The boss would get stuck inside a wall and I had to restart from the latest checkpoint.
The twist also felt like a "Got ya!" moment instead of an actually well done one.