2 hour preview:
http://www.ign.com/articles/2016/04/13/how-i-spent-two-hours-in-no-mans-sky-ign-first

21 minute IGN preview:
https://www.youtube.com/watch?v=D-uMFHoF8VA

Tl;dr shamelessly "repurposed" from around the web:

NMS is a resource-gathering survival game.

Everything is either consumable or perishable. You will be constantly mining minerals in order to do anything in the game. You need fuel to move, energy for your protective suit, ammo for your gun/multi-tool, upgrades need to be crafted with different recipes and different materials, etc...

New solar systems are gated. You need to find the correct ship upgrades, along with all the other consumable resources in order to just move around solar systems, never mind the entire galaxy. If you're attacked, you'll have to make repairs. If you die, you'll lose anything you were carrying on you and have to go mine it all over again.

There will be a lot of "WORK" in this game in order to explore it.

So, if you like farming and crafting in games, you'll love this game. If you find that stuff tedious and boring, well, you might be put off by it.