Cosmos is a popular science book written by author and scientist Carl Sagan. The book accompanies the award winning TV series of the same name.
The book treats a variety of topics: astronomy, cosmology, biology, physics, history of science, among others in a very interesting way. The author carefully explains every new concept thus being able to explain those difficult matters in a way that anyone can understand. The book is as visual as the TV series. It contains lots of pictures courtesy of NASA and JPL lab.
As the author was one of the world's leading scientists, he knew the subjects covered in the book from first hand experience. He even participated in some of the projects described, like the Voyager and Mariner space probes.