Note: I am not associated with the developers in any way, I've just been playing a lot recently.

Screeps is a game for programmers.
But it is possible for someone without any previous programming experience to learn it with enough dedication, though I recommend at least learning some basics of programming/JavaScript from somewhere like codecademy first. And try the free tutorial before you buy the game (I am still running code that started out based on the tutorial code, 2 months later).

The game has deceptively simple visuals, but a lot of increasingly complex systems that you gain access to as you progress within the game, providing interesting challenges for your programming ability. How complex it ends up getting depends in part on how much of it you end up wanting to automate. Pretty much anything you can do, you can get your code to do for you.

Like most programming, you are going to want to look things up in the documentation, which covers all the different elements your code can interact with, and has examples for most functions.
I also highly recommend joining the excellent and helpful community on the Slack chat.

I recommend that new players spawn in the green novice areas around the edges of the map, so that any combat you get into is at least with someone of relatively similar power to you, instead of getting wiped out on a whim by an established player. You will want to get a tower and some defensive code up by the time your safe mode ends, and remember you can activate another safe mode from your controller if you have any available.
Your main progression is your continued improvement of your code, most players respawn a few times.

As for what I think of the game, I love it!
This game has really reignited and fueled my passion for programming unlike anything before it.
The learning curve may be a bit steep, but that is part of the fun/challenge.
The community is great, and I spend a lot of time chatting on Slack and helping people with their questions and figuring out problems with their code. :) (helping people is optional of course, but I enjoy doing that)
The developers are pretty responsive, and are continuing to improve the game, and fix issues that may be raised by the players.

I find the subscription model fairly reasonable, and it is even possible to fund your subscription through your in game activities if you are reasonably good/developed. Though some choose to take on the additional optimization challenge of playing without a subscription and the additional limitations that gives.
Buying the game on steam also gives access to private servers, which is an alternative/additional way to play the game, and is a good place to test your code before deploying it to the live server.

Edit: A year later, I'm still really enjoying this game. It continues to get updates, and even some pull requests submitted by players get merged. Recently I have been enjoying implementing more complete automation in my code to participate in community-arranged bot arenas where players spawn into a small map with all interaction disabled except for the initial code upload, and the code has to do everything on its own and try to beat the other players' code at what ever the goal may be for the round. :D

Note: I am not associated with the developers in any way, I've just been playing a lot recently. Screeps is a game for programmers. But it is possible for someone without any previous programming experience to learn it with enough dedication, though I recommend at least learning some basics of programming/JavaScript from somewhere like codecademy first. And try the free tutorial before you buy the game (I am still running code that started out based on the tutorial code, 2 months later). The game has deceptively simple visuals, but a lot of increasingly complex systems that you gain access to as you progress within the game, providing interesting challenges for your programming ability. How complex it ends up getting depends in part on how much of it you end up wanting to automate. Pretty much anything you can do, you can get your code to do for you. Like most programming, you are going to want to look things up in the documentation, which covers all the different elements your code can interact with, and has examples for most functions. I also highly recommend joining the excellent and helpful community on the Slack chat. I recommend that new players spawn in the green novice areas around the edges of the map, so that any combat you get into is at least with someone of relatively similar power to you, instead of getting wiped out on a whim by an established player. You will want to get a tower and some defensive code up by the time your safe mode ends, and remember you can activate another safe mode from your controller if you have any available. Your main progression is your continued improvement of your code, most players respawn a few times. As for what I think of the game, I love it! This game has really reignited and fueled my passion for programming unlike anything before it. The learning curve may be a bit steep, but that is part of the fun/challenge. The community is great, and I spend a lot of time chatting on Slack and helping people with their questions and figuring out problems with their code. :) (helping people is optional of course, but I enjoy doing that) The developers are pretty responsive, and are continuing to improve the game, and fix issues that may be raised by the players. I find the subscription model fairly reasonable, and it is even possible to fund your subscription through your in game activities if you are reasonably good/developed. Though some choose to take on the additional optimization challenge of playing without a subscription and the additional limitations that gives. Buying the game on steam also gives access to private servers, which is an alternative/additional way to play the game, and is a good place to test your code before deploying it to the live server. Edit: A year later, I'm still really enjoying this game. It continues to get updates, and even some pull requests submitted by players get merged. Recently I have been enjoying implementing more complete automation in my code to participate in community-arranged bot arenas where players spawn into a small map with all interaction disabled except for the initial code upload, and the code has to do everything on its own and try to beat the other players' code at what ever the goal may be for the round. :D