The Mystery Dungeon series is part of the roguelike genre. This particular entry is half of the second entry of the Pokemon Mystery Dungeon spinoff. The other half being Explorers of Darkness, and there being a third entry, released later, Explorers of Sky, as is customary for the handheld Pokemon games. Some things never change.
Part of what defines roguelikes is a very high difficulty, random dungeons, and perma-death. Pokemon reduces the stakes a little by giving you a persistent character, and reduces the difficulty. There are still parts that are very challenging, and death causes you to lose all money and most items on your person. The question is less 'do I use this unknown item that might kill me' and more 'do I take my useful rare items to this difficult dungeon and risk losing it if I die'.
I've been playing it on and off for a few months, more off lately admittedly, but I recently picked it up with an aim to complete the story and 7 hours of item gathering and leveling up gave me the strength I needed to get through the last two dungeons. The last boss gave me some trouble, and I only brought barely enough revival seeds to keep me and my partner alive. But I got through, teared up at the ending, sat through the excruciatingly long credits, and started the post-story game.
It's here that the game gets a lot more difficult, and my first mission is to restore the ability to evolve Pokemon, which should help. I'm going to continue playing to try for a :C:, however unlikely, because I'm a obsessive masochist and I loved the hell out of it. 5/5 stars.