Deliver Us Mars follows the events of the original game, Deliver Us The Moon.

Although Deliver Us The Moon can be seen as a stand-alone game, with a contemplative story and bitter conclusion, the post-credits scene suggested the story isn't over, so here we are.

The events in the original game lead to a 5-year energy blackout on Earth, so now you play as someone from the first game (no spoilers), trying to discover what exactly happened on the Moon.

The gameplay is mostly the same: explore the bases and habitats on Mars, solve puzzles, scan things, and access holograms to get as much info as possible.
Most of the puzzles are beam puzzles, and now you have to solve a small "puzzle" to decrypt the holograms in order to view them, but overall, same gameplay.

The main difference is that now you can (and kinda have to) climb walls using 2 ice tools/axes.
Unfortunately, this is also one of the most annoying parts of the game, especially since the ice axes don't always stick, leading to a frustrating trial-and-error approach.
Also, while you still require oxygen, you forget you need it. There is no running to look for oxygen tanks or refill stations (in fact, those were removed from the game entirely), and it feels like any other action-adventure game.

Other than that, the game was enjoyable.
The story was well written and interesting, but while it does pose some interesting questions, it lacks the depth and contemplative nature of Deliver Us The Moon.

You also get memory flashbacks and cutscenes from your childhood, mirroring your current situation, something that somewhat reminded me of Life Is Strange and, while these were meant to show the character's inner struggle, it doesn't feel as relevant as it should. Especially since one of the main themes of the game is "family".

Another "problem" is that while the game focuses on family and tough decisions, you somehow feel disconnected since, in fact, there is no decision at all for the player. Everything happens in cutscenes, and it feels like someone else made that decision for you, something that can be frustrating, especially when you feel the decision is not OK.

There are also a few twists, but they are too predictable to make an impact.

The game also ends with a cliffhanger that most likely will reach its conclusion in Deliver Us Home.

In terms of gameplay/length, Deliver Us Mars is a bit longer than the original, with around 8 hours of gameplay, if you try to find every hologram, comic book, and scannable object.

Unfortunately, technically speaking, Deliver Us Mars has some issues.
The game looks OK, but it lacks polish; the character face animations are weird, and there are quite a few glitches.
Nothing game-breaking, but the game crashes more than a few times, especially on DirectX 12.
And, as mentioned, the climbing mechanic is kinda janky.

Overall, despite some obvious issues, Deliver Us Mars is still a great game about family and tough decisions, and a thoughtful and cinematic experience for the fans of story-driven games.