The rules are spread across a player manual, a rules manual and a scenario aid. Also, rules for the campaign and the individual scenarios are mixed in said books. It is not that intuitive at first. Once you play a scenario with the scenario aid by your side though, it all clicks and becomes more easier. There are still a few exceptions here and there that you must remember (most of them are on the player aid).
Then, when playing at a high player count, the hexes can become a bit crowded with loads of chits (ships, colonies, research tokens, planets, anomalies, etc.) You also have to adjust the dials every turn to indicate movement left for your ships, research level, etc. This can be hard to do without messing the state of the board even with the best intentions.
Now on the good side of things: the game is grounded in actual science and plausible technologies we might discover in the coming years. It feels "more real" and like you're going to neighboring solar systems to colonize them. But wait, can you colonize the planet you just discovered? Is the habitability level high enough for your faction and the tech you reasearched? Thinking about that, planning about your travels and the time it will take to get there, it's awesome!
All in all, once you understand the flow of the game, it shines and scratches the itch you didn't know you had regarding space travel and colonization!
