Book Shelf.

When it comes to how history works, there are two basic theories: Tolstoy's and America's. Tolstoy wrote that the soldiers and other actors of the Napoleonic era "imagin[ed] that they knew what they were doing and did it of their own free will, but they all were involuntary tools of history, carrying on a work concealed from them but comprehensible to us." The American theory, ingrained in our national character, is drastically different: The Mets won the 1986 World Series because Bill Buckner blew it. End of story.

The obvious corollary of the latter theory is that, in just about every case, the historical event in question could have turned out differently. This goes a long way toward explaining America's love of "counterfactual history"-essays and stories examining the "what ifs" of the past. The most recent attempt to cater to this taste is Almost America: From the Colonists to Clinton: A "What If" History of the U.S. by Steve Tally (Quill, 368 pp., $14). Each of the book's 28 chapters begins with the story of an actual event in the American past, up to a crucial point at which the author asks, What if this particular historical individual had chosen differently? Each chapter then gives a plausible account of the alternative America created by the counterfactual choice, and-necessarily, one suspects, in an age of historical illiteracy-briefly summarizes the consequences of the choices that were actually made.

The counterfactuals ring true to the extent that they reflect what we know about the real character of the people involved. The best case in point is the chapter on the impeachment trial of Richard Nixon. Tally asks, What would have happened if Nixon had decided to stay and fight? He proposes that Nixon would not have left the outcome of the trial to chance, but would have resorted instead to extreme measures-which, in turn, would have resulted in a further erosion of his political support and made his removal from office a certainty. What's especially satisfying about this idea is that it echoes the origins of the Watergate scandal in Nixon's own paranoid character: They were going to win the election anyway, but they felt compelled to make absolutely sure-so they made the mistakes that led, ultimately, to defeat. It's the plot of many Tom and Jerry cartoons, and reinforces a suspicion that character is destiny, after all.

A somewhat dryer recent book is Almost History: Close Calls, Plan B's, and Twists of Fate in America's Past, edited by Roger Bruns (Hyperion, 282 pp., $23.95). Bruns reproduces actual documents from various turning points in history; in these cases the alternative history came so close to becoming actual that it made its way into the primary- document paper trail. We find here, for example, the famous Robert E. Lee military plans that a Confederate officer had used as a cigar wrapper. (The plans were thus discovered by the enemy, who were forewarned of the deployments before the battle of Antietam. If the plans had remained secret, the South could conceivably have won a major victory in 1862.)

Finally, for those who like their alternative history with the accent on the history and not the alternative, there's How Hitler Could Have Won World War II: The Ten Fatal Errors That Led to Nazi Defeat by Bevin Alexander (Crown, 352 pp., $25). This book, too, is effective due to its grounding in the known facts of character: Hitler made his military errors because of the kind of person he was. Alexander writes, for example, that the German bombing of Britain was inflicting serious strategic damage in 1940. "Then, on the night of August 24, ten German bombers lost their way and dropped their loads on central London. RAF Bomber Command launched a reprisal raid on Berlin the next night with eighty bombers-the first time the German capital had been hit. . . . Hitler, enraged, announced he would 'eradicate' British cities. He called off the strikes against sector stations and ordered terror bombing of British cities." Because he was unable to govern his rage, Hitler traded a strategy that was working for one that only sparked the fighting spirit of the British. To say it could have turned out differently would require Hitler to have been a different sort of person; but a different sort of person wouldn't have created the bloody mess in the first place.