The Diamonds of Kronos — Andrew Dequasie

Other books have been written about battles between humans and creatures from outer space. So, what's different about this one?

Well, the aliens in this case know a great deal about planet Earth and its human population, but their info is disastrously out of date. It's a war in which tactics make all the difference and the aliens would have found peaceful cooperation a far more useful thing than the battle.

As a side issue, these highly intelligent aliens have evolved on a planet where oxygen and water are rare. Impossible? Not at all. The author's thesis on this point is that life can evolve anywhere there is an energy source the life form can use. In each case, the life form evolves so as to use the available energy source and, therefore, is very dependant on it, just as we depend on oxygen and water.