by David J. Griffiths. Widely considered the "standard" undergraduate text, known for its friendly language and manageable pace.
by Leonard Susskind. Designed for "amateur" physicists who want to understand the actual foundations of the theory beyond just popular science descriptions.
by J.P. McEvoy and Oscar Zarate. This book uses a step-by-step graphic format to introduce key figures like Planck, Einstein, and Bohr while exploring paradoxes like Schrödinger's cat.
~$15.99 at Barnes & Noble (Paperback) or ~$7.49 (eBook).