Wolcen is technically class-less, but there are three main archetypes: caster, rogue/archer, and warrior. Your character can equip any type of gear. You can learn every spell and ability, but abilities require specific weapons to use. For example, you can only cast spells if you use a staff or catalyst. The clever part here is that Wolcen has at least one 1H and 2H version for each archetype. So if you focus on one archetype, say pure caster, you can use the 2H weapon. But you can also combine 1H from two archetypes and use abilities from both. For example, if you use a pistol and a catalyst, you can use both archer abilities and spells. It's a very simple and intuitive system.
Abilities drop from mobs, sort of like POE gems, but you learn them permanently. If they drop again, you gain special currency when you learn them. You can equip 5 or so abilities. Equipped abilities gain experience and level up. As they level up, you unlock talents to modify the abilities like D3 runes. However, these options cost 1, 2, or 3 points (points available depend on ability level). This makes for a lot of different combinations. You can swap abilities and talents whenever you are out of combat.
There are no "primary" attributes. Instead there are 4 secondary attributes: Ferocity which modifies crit chance, Toughness for health, Agility for attack speed, and Wisdom for applying ailments (debuffs). Basically every weapon can do multiple types of damage, and you have a chance to apply an ailment based on the type of damage. You get an overall damage boost from your top 3 attributes. Every level, you get 10 points to distribute. You can reset this for a gold cost.
Wolcen has a skill tree very much like Path of Exile. Only it is much smaller and more focused. Fewer points, and easier to get to the edge, but each point feels like it does more. Wolcen also has the tree divided into rings, and you can rotate the rings so that you can pick which sections you want to focus on. Skills can be completely reset as well, for a secondary currency cost.
I am very happy that Wolcen allows you to respec and change abilities and talents easily. It makes it much easier to experiment, rather than having to start over all the time. I am terrified that Diablo IV will decide to be more like Diablo II and be a lot harder to change things.
There are some other interesting facets. The gem system is a bit more complicated, with specific socket types to get different effects. There's a built-in roll when you press space, which allows you to evade attacks and move around quickly. The basic attack has a built-in charge (which you can turn on and off if you don't want to charge). I really like these options because it means that movement abilities aren't "required", and you can take other abilities if you prefer.
Gameplay is pretty good. It's not quite as smooth as D3, but it's quite enjoyable. The bosses at the end of Acts I and II were pretty difficult. However, you can set the difficulty down to Story mode for just those fights, if you want.
I really like the story. I haven't finished it, I'm just starting Act III. But so far it's been solid, with pretty good voice acting. The female character models are a little weird (super long legs), but they look better in armor and in gameplay. Speaking of armor, I really like the armor design in this game. The cosmetic system is superb.
I'm currently playing a sword-and-shield tank, putting most of my points into Toughness, with a variety of buffs and debuffs. It's a lot of fun.
I should note that Wolcen has had a lot of server issues on launch. Most of which seems to have calmed down now. However, there's an offline mode which is completely functional. I've been playing in offline mode for the most part.
I don't know what the endgame is like, though. Apparently there's some sort of mode where you build up a city or something? I figure I'll worry about that when I get to it.
I am really enjoying Wolcen and highly recommend it. They've hit the sweet spot between simplicity and complexity almost perfectly. It's fun to fiddle around with all the options, try out different talents and builds, but still being able to respec whenever something isn't working out. The game looks good, plays well, and the story is interesting.
For me, the single player campaign is worth the money. If the endgame turns out good, that will be the cherry on top.