Is this a bad game? No.
But the question is not about the quality it’s about recommendation. And sadly I can’t clearly recommend Munin.
I like the indie logic-platform games, but the Munin can’t grab me. The game doesn’t have serious flaws but it hasn’t got any serious pro either. For me games like Braid, Limbo, Thomas was Alone give more.
Munin hasn’t got great atmosphere, unique visual style or soundtrack either. The puzzles are not very interesting. Basically it’s like a dumbed down FEZ. The only thing was stand out a few annoying puzzles where you easily can die because the deadly “lasers” reflect from mirror to mirror. You won’t know how you can rotate the platform until a few amounts of trial and error.
However the game is longer than the average indie platformer I give it that. The rest of the games what I mentioned is takes around 2 hours to complete. The duration of Munin is ~6 hours.
In the end I only recommend to the hardcore fan of genre. For everyone else there are far better games you can try out.