"History is not merely what happened."

"History is not merely what happened.  It is what happened in the context of what might have happened."
- Historian Hugh Trevor-Roper, as quoted in The Independent.

We are fascinated with today because we don't know what tomorrow will bring.  The same cannot be said for yesterday, whose outcome we already know.

That's why history is boring.  History becomes enchanting, however, when you consider what could have happened.  These three books by Robert Cowley are full of alternate histories:

What If?: The World's Foremost Military Historians Imagine What Might Have Been
What If? 2: Eminent Historians Imagine What Might Have Been
What Ifs Of American History