Lots of excellent analytic articles out there right now on the current crisis in Ukraine. Here are a few:
A lengthy, detailed "how we got to this situation" piece from "Der Spiegel", [in English], here.
This, from James Sherr, about the flaws in Putin's imperialist policy
And this from Lilia Shevtsova from the Carnegie Moscow Center about possible unintended consequences of Putin's game plan
Also "Putin’s Phony War - How Vladimir Putin concocted a conflict to soothe his own paranoid fears."
"Convinced that the new authorities in Kiev will finally pull Ukraine out of Russia’s orbit, Putin is hacking off as much of the country as he thinks he can get away with. He doesn’t want to re-create the Soviet Union as much as form a ring of buffer territories to ward off Western influence from the Russian heartland. For Putin, it’s the beginning of the endgame for his regime’s survival."