There is a lot to learn but that's part of the charm. You become better by learning things, there is no difficulty scaling or whatever, and you don't gain stats. You just get better at the game. This is why Shiren is much more interesting than all other modern roguelikes.
You can play the first one on DS if you want. I don't know about this one, but I thought it was supposed to go back to simpler mechanics. It should be much less overwhelming than 5+.
Buy Chocobo's Mystery Dungeon EVERY BUDDY! and shop other great Nintendo products online at the official My Nintendo Store.
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Very friendly to people new to the genre, and a fun Final Fantasy coat of paint on the characters, monsters, items, etc. Also currently on sale for $16.