Definitely a ton of fun. I only played the first one until about level 15 (Unlock Ronin) before life got in the way and it was put down. I recently got Untold and it has been fun, completely different storyline too.
The game is NOT easy, especially if you don't do some grinding you will quickly find yourself deep into higher leveled territory than you should be, leading to game overs. Save often.
Looks like I missed release of another Etrian Odyssey.
From what i read now - it is basically remake of EO I with lots of improvements. But some moments are a bit obscure.
Is there same dungeon for Story and Classic mode? In other words - do you need to play through both - Story and Classic in order to see all content (except story)?
Is there still retirement system (might be wrong on its name)? Where you have level cap at around 65, and then need to downlevel character back to 1 to increase level cap?
Were additional (deeper) floors added to dungeon (I assume it is same dungeon as in EO I?)?
They are hard as hell, I'd say start with the first game in the series since the 3DS is backwards compatible, might take some time to find a copy though. I tried the demo of 4 and it was really quite challenging even on normal mode.