Timothy Snyder is a historian who has written on extensively on the history of Ukraine (Bloodlands) and Putin (The Road to Unfreedom).
I'm not familiar with The Tragedy of Great Power Politics, but Dr. Snyder makes some strong counterpoints to the Mearsheimer way of thinking on Ukraine in this [1] podcast and others.
He has also given a timely history on modern Ukraine [2], but I have not got around to listening to it.