I wanted to buy it when the xbox one came out, it looks really boring though.
It can be, I started with a harder difficulty right off the bat, cos nothing makes a stealth game more boring than AI that is completely oblivious and incompetent. My first playthrough took 35h and I enjoyed it very much. I played it through again in 4h (speed run for an achievement), but I didnt stop to do anything other than 100% required parts of story. I still had plenty of explore and find (mostly collectibles) but I didn't feel like hunting them all and I sold the game while I got a good deal for it. But if I had to wish for one game to get a sequel right off the bat, Thief would be right up there with Titanfall for me. Thief has/had quite a few technical problems though, there are so totally unexplainable FPS losses (not related to Xbox One) and in a few areas the gameplay gets pretty stuttery.
Overall I recommend picking it up for that price if you are at all interested in stealth games. The thing I like about thief is that it has no emphasis on killing, so you can go like 100% stealth if you want or you can have a more liberal approach. Storywise Garret tries to avoid killing as much as possible, I kinda played in that same way, I only killed if I kinda had to (or then I just loaded the game again and tried to stealth it away again) but I sure knocked people out in a liberal fashion
But essentially it's up to you, if you want a more combat based approach, it's totally doable and can be enjoyable too. There are a lot of skills around bow usage for example. The game also puts you in a place where you personally get to choose whether you kill or flee in the story.