Seriphyn*
Yes it's worth 10 euros, it's also getting constantly updated, for free, like the next update on the 31st.
The solitude of the game is very enjoyable, and it's one of those "story" games in the sense you can tell your friends "Well first I was a, then I was b, after that I did c, but I fell into a pit and was at d, traced all the way back to e" and so on and so forth.
The world is MASSIVE and goes on and on, but unfortunately you spawn at your original spot, so you'd want to build your shelter near there. If you do go on expeditions, only take limited stuff and all that. The cave system is particularly intricate as well, some of them just seem to go on and on, downwards. You'll want to place torches to light up the area as you go, to prevent monsters spawning there in darkness. Sorta represents "charting" it.
There's a lot to say, really, but definitely worth the 10 euros.