Military science fiction master David Drake's two technothriller Tom Kelly novels "Skyripper" and "Fortress" in one volume.
"Skyripper"
During the Cold War, a Soviet scientist has knowledge the Earth will be attacked by aliens, but only the U.S. has the laser-based technology to knock out the alien weaponry. Enter Tom Kelly, American spy, navigator of the U.S. intelligence agency spaghetti, and ruthlessly effective operative when it comes to doing his job. Kelly will get the information into the right hands to save most of humanity - but in the process, he's prepared to annihilate anyone who gets in the way of his duty.
"Fortress"
Tom Kelly and his ruthless, adventurous ways return in an alternate past as JFK builds a space station to guard against alien attack. Now nefarious forces with the Soviet Union as well as actual, evil aliens are trying to turn it against Earth, and the U.S. THEY may have the high ground and the element of surprise on their hands, but WE have Tom Kelly. For better or worse. Or both.