Papers

• On the concepts of the special theory of relativity
  
  

Books

• The Age of Einstein by Frank W. K. Firk. This is a free introductory book on the special and general theory of relativity.
  
  
• Electromagnetic Field Theory by Bo Thide. This is a free graduate level textbook with a chapter on special relativity and the relativistic formulation of classical electrodynamics.
  
  

References

1. W. Perret and G.B. Jeffery, The Principle of Relativity: A collection of original memoirs on the special and general theory of relativity, with notes by A. Sommerfeld, Dover Publications, 1952.
   
   This book contains translations of original papers by H.A. Lorentz, A. Einstein, H. Minkowski, and H. Weyl. Einstein's famous paper, On the electrodynamics of moving bodies, published in Annalen der Physik, 17, 1905, is included.
   
   
2. A. Einstein, Relativity: The special and the general theory, Translated by Robert W. Lawson, Random House, 1961.
   
   Written by Einstein himself, to provide a popular exposition for "those readers who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics."