For Want of a Nail : If Burgoyne Had Won at Saratoga (1973) is a dry and exhaustively footnoted textbook for a survey course in American history - written in an alternate universe. An exhaustive, and totally straightfaced, apart from the title, look at history since John Burgoyne defeated Horatio Gates at the Battle of Saratoga, and Great Britain's subsequent victory in the abortive American Revolution.
Of course, the basic idea is not terribly original, but the almost unthinkable detail that the author, Robert Sobel, an actual historian who's obviously written his share of honest-to-god history books, goes into is impressive. The bibliography is thirty pages long, thirty pages of books never written and put out by nonexistent university presses, drily documenting decades of imaginary academic infighting and historical revision. The effect almost succeeds too well, at times; it's pretty easy to forget that you're reading a work of imaginative fiction (or imaginative something), and get that familiar eye-glaze from reading another goddamn history book. You feel like you should be highlighting the parts that'll be on the exam.
Sobel's premise is that after the collapse of the revolution, the most hot-headed of the revolutionaries lit out west for Texas, which they founded a new nation in, calling it Jefferson after their executed hero. The American colonies are united with Canada, and eventually granted dominion status as the Confederation of North America. Jefferson, meanwhile, eventually forms an unstable and ethnically tense union with revolutionary Mexico as the United States of Mexico. The latter part of the book is a chronicle of the diverging social and industrial development of the two nascent countries, and the eventual, tense, cold war-style standoff they arrive at.
The end result is a sort of puzzle box of a book: Who would write a college level history book of events that never happenned? Why am I reading this for pleasure, even though I'd never read a regular history textbook for kicks? It's not really possible to comment in any meaningful way on how likely the events of For Want of a Nail are, except to say that Sobel has certainly made his case in great detail.