I can't recommend anything written by Dirac as an introduction to the concepts in Quantum Physics.
The two most common textbooks for a beginner (which include exercises) are "Quantum Mechanics" by Alastair Rae. (most recent update 2008) and
"Introduction to Quantum Mechanics" by David Griffith (Most recent update 2004).
Both books cover near identical material, but have different examples and different approaches.
From there, a good continuation point would be "Introduction to Elementary Particles" also by David Griffith.
Finally, after all that and you still want more, I'd recommend An "Introduction to Quantum Field Theory" by Michael Peskin and Daniel Schroeder, this book covers the same material that Dirac's book, but is considered a lot more approachable. If you somehow get through all this, you know more Quantum Physics than most Physics graduates.
As a matter of fact, Peskin and Schroeder is reading material for people taking their Theoretical Physics PhD!
This post imported from StackExchange Physics at 2014-06-14 13:21 (UCT), posted by SE-user Matt Scott