The short version:

Ember Knights is just fun, the kind of "just one more run" kind of fun. There is a shocking amount of variety between the different weapons, weapon customization, skills, and relics. Each run does not overstay its welcome, but if you want to keep looping to see how strong you can get then that door is open to you. For the price, game it totally worth it.

The long version:

The good:
Not only does each weapon in the game have its own unique feel and cadence to its combat, but you get more customization options and you unlock more abilities for each weapon, leading to a wide range of unique experiences. This is the real meat of the content in Ember knights. I personally love the scythe, bow, and new buster weapon from the DLC.
Skills are a bit special in Ember Knights, with most being completely divorced from the weapons. I will admit, waaaay back at the original launch, the skills sucked. Like two were viable and one was good. The developers took the feedback and completely overhauled the skills system, making it almost as robust as the weapon system. It feels so good to weave normal and perfect skills between weapon uses now. The skills now also have their own unique upgrade trees that you can unlock before each run (though you have to select them during the run as you get the skill selectors).
Relics are the passives that you use to improve yourself over the course of each run. If you have played any rouge game, then you understand how these will work and stack. There are a ton of them, but not enough to be overwhelming. It is a well done execution.
The zones are all pleasant to look at with many having little hidden pockets of healing or gold. They contribute to the combat without getting in the way. Each zone in the game even has a fun secret to figure out (or just look up).
The enemies/bosses feel well designed, where individually they are not very hard, but start comboing together to pose an actual threat to you. The bosses are especially good, where raw knowledge makings perfecting them possible even with base character abilities (as the new boss rush mode proved to me).
The difficulty follows the now tried and true Hades pact of punishment method. You control the challenge the game provides and make it increasingly harder until you see everything the game has to offer.


The bad:
This list is much shorter, but still should be covered. First is how the game can have a lot of visual noise. Even solo, the screen can be covered with explosions and effects to the point you get lost in them. Second is how the game wants you to "perfect" weapon abilities and skills for bonuses, which is often almost impossible due to how the monsters stagger their attacks and how the screen gets covered. Third is how the builds of weapons and skill slowly homogenize over the course of the run. Due to the number of relics, your builds will start to feel similar as your approach the final boss. If you end up looping, eventually you reach a point where your run is literally the same.


The DLC.
Wrath of the Architect just came out at the time of this review. It adds a ton of new content, to the point where I would say it make the game 50% larger. It is worth it, but there are some disappointments. Many of the new biomes have rooms that feel like pure re-skins of their alternate world. This can be explained with story, but some new layouts would have been appreciated. Many of the new enemies really work to punish melee builds. You can still win, but you have more downtime trying to find windows of opportunity so it is not as fun. My main issue, however, is the final boss. Looks like a total baddass, weakest boss in the game, like base mode Praxis is harder. I mean, the boss spends a third of the fight afk, another third covering the screen with easy to dodge AOE (except when he shifts to the spider stage, then he will instant cheap shot under you if you are not spamming roll right/left), and the final third punching the ground on the other side of the screen. He summons some adds, but all but one of them are so basic they will die in two seconds. The new boss needs a hard mode, make him summon the new mini-bosses, make him seal your skills, make him use your weapons against you. Something to make it an actual challenge.

The closest thing to co op Hades. Maybe even better.

mega underrated, super fun