You simply are not going to find a more concise, clear, and effective summary of the causes of the Cold War and its first decade than this one. In about 150 pages, Leffler walks through the roots of this conflict mainly from the US perspective, but he skillfully incorporates the secondary literature from the USSR, Great Britain, and other critical countries in this history. He moves along quickly but with enough depth to give you a bit of color and a clear sense of motives, perspectives, etc. He does one thing I really like in Cold War history: describing how the participants interpreted each other's motives and actions but then explaining what "We Now Know" through recent releases of documents and historical work. Obviously Gaddis' book of that title is the gold standard on that topic, but you can get a very similar treatment from Leffler in 1/3 of the time.
Here are a couple of the major themes from this book, or at least some new things I picked up. For Leffler, it is obvious that the US would be hostile to the USSR, and vice versa, for cultural, ideological, political, religious, etc, reasons from its inception. To get a Cold War, though, you needed the expansion of Soviet power and the ability to threaten vital US interests. After WWII, the US leadership believed that key regions of the world like Europe and Japan needed to be rehabilitated and integrated into a more open global economy and political order. The immediate postwar threat wasn't so much a litany of aggressive Soviet actions (although they certainly were brutal and extractive in their treatment of Eastern Europe) but the possibility that the failure of places like Western/Central Europe and Japan to recover from the war would create openings for communist infiltration or neutralism. The greatest fear was that the Soviets would gain the resources of an entire continent (either Europe or NE Asia) and project that power against an isolated US. As a side note: I really got from this book why the US saw SE Asia as so strategically critical: with JP surrounded by Communist states on all sides, the possibility of SE Asia falling as well would leave JP isolated and probably force it to drift toward the Eastern Bloc, creating the specter of a continent under communist control.
The US, Truman and others thought, would then have to become a "garrison state," a permanently and heavily armed country mobilized for war at all times and, ultimately, a less liberal and democratic society. The Cold War was originally conceived as a way to avoid that outcome. Of course, Leffler goes through the back and forth of escalating events and perceptions, including Stalin's remarkable blunders based on his belief that the US would be endlessly understanding of his need to ensure friendly countries along his border. I still kind of think the Cold War was largely the Soviets fault (I know that's not a very historical question), but Leffler does a good job skirting that question and unpacking the steady escalation of this conflict and the US adoption of the role of hegemon, which despite its negative connotations really means a predominant power that guarantees some kind of order in a region. He duly notes that US hegemony was far more negotiated and consensual than the cage of Soviet control.
This is a book I might assign to an undergrad class on the Cold War, although it might be a bit old at this point (1994). I will definitely reference it a lot in my own research as a reliable and concise guide to a complicated topic.