Our Darker Purpose is a gorgeous game in many ways. The way the story and setting is drip-fed to you via talking desks or boss descriptions allows you to engage with it or get on with the gameplay itself, and the writing manages to be funny without being cringe-worthy. The music is also truly amazing, perhaps the best I've heard in any indie game.
I find the gameplay particularly engaging as well. On the surface it does hug closely to Binding of Isaac gameplay, with randomised rooms, unlockable items and locations, starting over when you die etc. But it does go beyond that. The emphasis on choice over randomness is far more evident in ODP: Each time you level up you choose between two perks that may boost your attack or survivabilty in some way (life leech, attack speed, or some more exotic perks), and you unlock lessons that you can equip before a play-through that can have a dramatic effect on your gameplay. You can also choose which floor to enter after a boss battle, and each floor may have different enemies or modifiers to them (enemies will drop more juice boxes, won't have champion enemies, you and the enemy will take more damage etc.)
These elements allow for less of a feeling that the RNG was against you, and more that if you die you messed up in some way. It also means that even if you are having trouble, you may unlock lessons that will help you in the future, so there is always a small sense of progression without making the early levels feel trivial.
One downside to the game is that earlier areas can feel repetitive, as there is a smaller set of potential enemies and items that you will encounter. Earlier levels can also look a little too grey for my liking. It also isn't clear how to unlock each of the lessons - something I find frustrating but other people may enjoy discovering the unknown.
Over all its a good game to play for several hours in a row or just half an hour, and its easy to sink at least 30 hours into the game (for those who care about replayability). And the music is to die for - that cannot be said enough!