• Daniel I. Khomskii: Transition Metal Compounds (online via HEIDI)
• A.H. Morrish: The Physical principles of Magnetism. Reprint from 1965. Detailed and good description on magnetism. Sometimes old notation, but recommended both for introduction and research.
• W. Nolting, A. Ramakanth: Quantum Theory of Magnetism. Comprehensive theoretical introduction into magnetism. Good theory textbook.
• P. Fazekas: LECTURE NOTES ON ELECTRON CORRELATION AND MAGNETISM. Very good theory book bridging back magnetism to electron correlations. High level (but also good for experimentalists).
• N. Majlis: The Quantum Theory of Magnetism. Textbook for a theoretical condensed matter magnetism course. Sophisticated
• Daniel I. Khomskii: Basic Aspects of the Quantum Theory of Solids: Order and Elementary Excitations (Table of contents)

Literature on group theory in solid state physics

• M. Tinkham: group theory and quantum mechanics
• M.J. Lax: Symmetry principles in solid state and molecular physics
• Powell, Richard C.: Symmetry, Group Theory, and the Physical Properties of Crystals (fulltext online available via HEIDI)
• Dresselhaus, Dresselhaus, Jorio: Group theory. application to the physics of condensed matter, Springer 2008 (incl. crystal field splittings etc)