A description of the elementary concepts of superconductivity, and a discussion of flux-lattice melting, magnetization including the para-Meissner effect, microwave absorption, a.c. resistivity along with the London penetration depth, the Mossbauer effect, levitation, fractals and nuclear magnetic resonance. There are appendices covering superconducting compounds, the isotope effect, symmetries, the pseudogap, relativistic superconductivity, the Cherenkov effect and soft vortices. Also included is an appendix on the quantum Hall effect. In all of the chapters, the theoretical description is supported by experimental data.