It's taken me about 3 or 4 restarts to get to grips with the base building (that is, how to make a base that's not going to end up getting everyone killed because you're still working on the walls by the time enemies show up, lol) It's harder than it looks if you're trying to keep your dwarves alive, but if you don't really care, then you'll have a lot of low skilled dwarves about and gradually be able to progress through a sort of 'war of attrition' approach, since it seems you get new dwarves over time, and most enemies die at dawn so they wont simply camp your newbies as they spawn in.
Many people have asked me if the game's any good after seeing me playing it on steam, but I'm always reluctant to recommend a game because what's good to me may very well not be good to anyone else. So understand that what I say next is purely from my own perspective, and your mileage may vary... but, although certainly casual, so far I've found this to be the good sort of casual. Just enough that you need to be doing to keep you busy, but not so much as to force you to have to sit and plan your next moves carefully lest you ruin everything.
I've found myself playing the game for a few hours at a time and wondering where the time went, though that in and of itself isn't always a good thing, I can clearly remember why I enjoyed my time on it after the fact. That's usually my litmus test, if you will. If I can't recall, or explain what it was I was enjoying, then it's probably due to some sort of game design witch-craft involving spoon feeding me delicious 'achievements' to keep me clicking, and keep me distracted from the fact I'm wasting my life xD