Doomsday Conspiracy
In 1992 Sidney Sheldon threw readers a curveball. He wrote a science fiction book. Aliens decide to invade Earth. They are mad about the damage people have done to it. Also this book centers on a man, a departure from his usual female protagonist.
Robert Bellamy works for the Navy. He is assigned to track down a weather balloon that has crashed into the ocean. He tracks down witnesses who quickly begin dying after he talks to them. It turns out the whole incident is an international conspiracy.
The final battle will take place in the Alpines. This book has a bit of suspense and message. May not be for the reader who loves Sidney's other books. But a nice switch nonetheless.