This book is considered an Introductory Quantum Mechanics textbook that presents relativistic quantum mechanics to interested learners with no previous knowledge of it. The authors only refer to the Klein-Gordon and Dirac equations to justify the use of the Poveda-Poirier-Grave de Peralta (PPGP) equations, upon which this book is solely based (while sporadically referring to well-known results obtained using the Klein-Gordon and Dirac equations to avoid unnecessary complications in an introductory book).