No shame putting down a book you're having a hard time getting into. That's something it took me longer than it should have to realize. There's a lot of books out there, and if one's not working out, no one's keeping score on how many you finish. I'd recommend following your gut and trying the Mars books first. If it turns out you like KSR, maybe you might find yourself coming back to Ministry, and in a different frame of mind. Or you might find you actually don't care for KSR even after trying Mars, and then you can move on to other books without worrying you're missing something.