W. Greiner: Relativistic Quantum Mechanics (Wave Equations)
Here are some notes on the book W. Greiner: Relativistic Quantum Mechanics (Wave Equations); 3rd Edition, Springer-Verlag (2000). The book contains no exercises for the reader (well, there are exercises, but the solutions are given in detail in the book), so I'm providing only my own notes on the text to summarize the contents and clarify a few points. On the whole, though, Greiner tends to provide detailed derivations
of most of the results, so there aren't many steps to fill in.
Chapter 1: Relativistic Wave Equation for Spin-0 Particles: The Klein-Gordon Equation and its Applications