Time's Eye: A Time Odyssey Book One by Sir Arthur C. Clarke
1885, the North West Frontier. Rudyard Kipling is witness to a British army action to repress a local uprising. And to a terrifying intervention by a squadron of tanks from 2137. Before the full impact of this extraordinary event has even begun to sink in, Kipling, his friends and the tanks are themselves flung back to the 4th century and the midst of Alexander the Great's army. Mankind's time odyssey has begun.
It is a journey that will see Alexander avoid his premature death and carve out an Empire that expands from Carthage to China. And it will present mankind with two devastating truths. Aliens are amongst us and have been manipulating our past and our future. And that future extends only as far as 2137, for that is the date Earth will be destroyed.
This is SF that spans countless centuries and carries cutting edge ideas on time travel and alien intervention. It shows two of the genre's masters at their groundbreaking best.