"X President" by Philip Baruth was an interesting exploration of unintended consequences. The book focuses on Bill Clinton's legacy - the interaction of his Tobacco Accord that resulted in a settlement of billions of dollars to states but allowed the companies to export to the rest of the world, and the expansion of Nato to former Warsaw Pact countries.
Sal Hayden, Bill Clinton's biographer in the year 2055 travels back in time with NSC agents coded named "George Stephanapoulos", "James Carville" and "Virginia" (BC's mother's name) to change the unintended consquences as the United States finds itself losing a war with China and Russia.
I thought the book was even more interesting now with the resurgence of Russia. It does make me think twice about what I had said about unintended consequences.