In 1939, Winston Churchill called Soviet Russia "a riddle, wrapped in a mystery, inside an enigma." Not a bad description of North Korea today.
While there are exceptions in history, I generally believe that nations and their leaders are rarely "crazy," meaning stupidly irrational. Usually they act in pursuit of some important national interests, even if outsiders consider their actions puzzling or worse. On the other hand, outsiders have a tendency to "mirror image," to assume that others make cost-benefit calculations and visualize political contexts as they do. [Why didn't the North Vietnamese give up in response to heavy American bombing?]
I want to believe that the North Korean leadership is rational, that regime survival is its highest goal, and that it will not risk survival by starting a new war with the United States and South Korea. On the other hand, there are too many examples -- July 1914 being the best documented -- of miscalculations leading to a spiral into terrible war.
I guess we have to watch the evidence for signs that might point either way when it comes to North Korea.