
Past and Present
Some contributors suggested Harry Harrison's A Transatlantic Tunnel, Hurrah!
There are a several of other terrific alternative history novels: Ward Moore's Bring The Jubilee (the North loses the Civil War); Keith Roberts's Pavane (the Spanish Armada is successful; England returns to the Catholic fold); and PK Dick's The Man in the High Castle, in which the Axis Powers win the Second World War - it's a zillion times better than Robert Harris's feeble rip-off, Fatherland.
And as for future history, you cannot do better than the truly fantastic stories by Cordwainer Smith.