I genuinely recommend reading the book, it won't take you that long.

Key points I got are:

1. Summary of the US policy toward Russia post USSR up to present

2. There is a history of NATO moving east, and also a history of US weapons testing near the border and backing out of nuclear and arms treaties.

3. Preliminary integration of Ukraine military and economy prior to any admittance into NATO, effectively making them an arm of NATO without formal admission

4. A bunch of other history which contextualizes things. Seriously good extra context if you are not familiar with the history.

5. Ultimately, the US and NATO are far more at fault for the tensions that led to the current crisis.