Steamworld Dig 2 is the sequel to the first Steamworld Dig title, which was a pretty great platformed where you go down instead of up. This creates a different dynamic to most games in the genre because you can usually tell what comes ahead and going back is generally harder than pushing forward so the player has to dig carefully in order to optimize their path through progressively more difficult sections of the mine.
Steamworld Dig 2 is very similar, only with better graphics, more enemies, different upgrades, etc. There's a greater emphasis on story this time around as well and I think it's decent and ties in some loose ends for the Steamworld series as a whole so that's nice.
Something I didn't like is how there are different branches to the levels, so to speak, rather than a single mine shaft that goes impossibly deep. In the first game I felt like that added a sense of mystery to the exploration because every step took you further away from civilization and into the increasingly dangerous entrails of the Earth.
Steamworld Dig 2 has a lot more level variety, but I believe the trade-off was a loss of the sense of progression the first game had (especially towards the end). However, I recognize that this is a subjective preference and the new biomes look really nice.
To conclude, I think I would recommend Steamworld Dig 2 to pretty much anyone. It's short, polished, easy to pick up and the presentation is really good. Although perhaps it would be wise to play the first game first in order to understand the story better.