Very interesting and complex, certainly not suited for a newbie in strategy games. Stellaris is probably the most awesome game i've tried in years: there is always something new to learn, the tech tree is nearly infinite, customizing your race to start taking over the galaxy is really fun, kinda like building your character in an RPG game, even though this is a strategy game, and the space battles are just incredible. Plus, if you ever got to build a titan and use it...oh, man! I just can put down in words the feeling of destroying a planet like Tarkin did in SW...you will have to try it yourself.
Only one flow: it's reeeeally difficult to understand. It lacks a guide, so you will need a few days to finally keep up the pace with AI, but once you do you are probably ready to get to the end game. I recommend to buy some DLC too, they are really worth it.