Chapter 1 Superfluid Liquid Helium and Weakly Interacting Bose-gas: Bose- Einstein condensation and neutral superfluids He4 and He3; Charged bosons in two dimensions. Chapter 2 BCS Theory of Superconductivity: BCS ground state and excitation spectrum; Hallmark indicators of BCS superconductivity. Chapter 3 Intermediate-coupling Generalisation of the BCS Theory: Effects of the electron-phonon interaction in a normal metal Migdal approach; Intermediate coupling superconductivity Eliashberg theory. Chapter 4 Many Polaron Problem: Breakdown of the Migdal approach in the strong-coupling regime; Canonical transformation and exact eigenstates in the strong-coupling limit; Spin polarons and bipolarons. Chapter 5 Strong-coupling Bipolaronic Superconductivity: Polaronic superconductivity; Bipolaronic superconductivity. Chapter 6 Non-Fermi Liquid Features of High-Tc Oxides and some Theoretical Proposals. Chapter 7 The Bipolaron Theory of High-Tc Metal Oxides: Earlier indications for mobile polarons and bipolarons in oxides; Effect of the Bose-Einstein condensation on the infrared absorption; Superconducting state thermodynamics and kinetics. Part contents.