This book presents and develops a theory for unconventional superconductivity driven by spin excitations. Using the Hubbard Hamiltonian and a self-consistent treatment of the spin excitations, the interplay between magnetism and superconductivity in various unconventional superconductors is discussed. In particular, the monograph formulates a theory for Cooper-pairing due to exchange of spin fluctuations applicable for the case of singlet pairing in hole- and electron-doped superconductors, and for triplet pairing in Sr2RuO4. Within the framework of a generalized Eliashberg-like treatment, calculations of both many normal and superconducting properties their elementary excitations are performed. Also included are the phase diagrams of the materials which reflect the interaction between magnetism and superconductivity.