It's already obvious that the full release will have some type of single player campaign beyond the tutorial and looks like it will have new single player scenarios rolling out all the time.
The multiplayer is the only thing that's basically fully fleshed out right now, but it's fun too. I would dive into this right now if I weren't worried about progress being reset when the game goes into full release. You can collect minis to use in building your warband. The more you level up the more points you have to spend on which figures can be in your warband at a given time.
Honestly, it feels a lot like some tabletop tactical mini games that I've sampled over the years... but digital! I like it a lot and will definitely be coming back to it once it's officially complete and fully released.