This book is an introduction to quantum mechanics for undergraduates and interested lay persons. The presentation is both reader-friendly and complete. The first four chapters cover the conceptual and philosophical aspects of quantum mechanics, before the next eleven chapters gently present the mathematics underlying the subject. After a chapter on the history of the theory, the whole of quantum mechanics is then presented. This is followed by applications of the theory and a revision chapter, before we briefly look ahead at relativistic quantum theory. 1. The Place of Quantum Mechanics in Modern Physics 2. The Dynamic Variables in Quantum Mechanics 3. Wave Particle Duality, Superposition, and Non-Locality 4. Complex Numbers, Wave Equations, and the Momentum Operator 5. An End to Determinism 6. The Newtonian Wave Equation 7. Linear Spaces and Inner Products 8. Operators, Eigenfunctions, and Eigenvalues 9. The Place of Operators in Quantum Mechanics 10. Commutation Relations in Quantum Mechanics 11. Angular Momentum and the Position Operators 12. A Note on Entanglement 13. Expectation Value and Standard Deviation Worked Example 14. Probability 15. The History of Quantum Mechanics 16. Quantum Mechanics An Overview 17. Basic Formulae 18. De Broglie Waves Lead to the Momentum Operator 19. The Hamiltonian and Schr?dingers Equations 20. Boundary Conditions on Eigenfunctions 21. Wave Mechanics - the Schr?dinger Equation 22. Solving the TISE in Several Potentials 23. The Free Particle Solution of the TISE 24. The Infinite Square Well Solution of the TDS 25. The Step Potential 26. The 3-Dimensional Box and Degeneracy 27. Parity 28. The Simple Harmonic Oscillator 29. Angular Momentum 30. The Stern-Gerlach Experiment 31. Intrinsl6