Sarafan: I have this game in my library, but never played it. :) What's the difficulty level like?
There are 4 difficulty levels, affecting things like how many aliens you have to deal with at a UFO site, how quickly you have to deal with more advanced aliens etc. On the easiest level it is very forgiving and on the hardest difficulty it's pretty insane. Which is fitting as the latter difficulty level is called 'insane' :) But regardless, you can also save anytime if you don't pick ironman mode, even during ground battles.
Apart from that how difficult it is will depend on how comfortable you are with games in the genre. It's a lot like the original X-Com: UFO Defense game, only better I'd say. If you want to check it out just be sure to install the Community Edition mod for some much needed quality-of-life improvements.