Love survives time and distance
Although a history-oriented reader will not be disappointed by this letter collection in terms of historical importance, the major theme of the letters seems to be non-political in nature. They write because they genuinely miss each other, both as romantic partners, but as friends. They seem to thirst for their long conversations, and they speak to each other very intimately, even when John Adams is months away in Europe, even when America's journey to independence seems especially dark and distant. Their love survives the entire journey of John Adams's political career, wherever it took him.
The emergence of America as a nation
This book features a loving, passionate, committed couple, and although it's not literally their "child," something is born in the book—America itself. During the course of their letter writing, we see John Adams decisions to pursue independence, the strategy of recruiting representatives from the states for the Continental Congress that penned the Declaration of Independence after voting to withdraw from British rule. We see John Adams during the Revolutionary war, as a political target in wartime, and then we see him serving the fledgling American state as a politician.
The value of human life
John Adams's opinions about political theory and philosophy are highly influenced by the high valuation of human life. For the early Americans, the reason they believed their exit from British rule was morally correct was that the British had shown (through tyranny and bad decision-making) that the British government held a low view of human life, at least the lives of the Colonies.
By reasserting that human life is universally valuable, as an unalienable property of their existence, John Adams and others gradually moved toward a Greek/Roman government, with representation for the people in a three part government. Famously, the issue of human sovereignty and divine value is a critical part of the Declaration of Independence, so he tells his wife about these ideas, in real time.
