Richard Feynman's Lectures on Physics
have achieved pretty much legendary status.Six Easy Pieces
takes six of these lectures to provide an introduction to the subject for the beginner. These are include a description of how everything is made of atoms, which in turn are made up of smaller particles, a look at the relationship between physics and the other sciences, and a study of the consequences of the conservation of energy. The book concludes with chapters on the theory of gravitation, and on the mysteries of quantum theory - in particular the implications of the two slit experiment.
The thing is though that while the Lectures on Physics are still a valuable resource for those wishing to learn physics, I would think that if a beginner needs motivation, then it should be something more up to date - these lectures were over 30 years old when the book was published, and predate black holes and quarks. This book may have value to those trying to decide whether to invest in the full Lectures on Physics, and to those wishing to study Feynman's style of lecturing. However, I would suggest that anyone wanting an introduction to modern physics would do better with a more recent work.