This website accompanies the two books "Electronic Structure" and "Interacting Electrons". It contains mainly older material concerning the "Electronic Structure" book, and new material focussing on the topics of the second book, "Interacting Electrons", and related information. It will evolve in time, and it will allow you to directly access material such as small scripts for models, or links to tutorials. Therefore, its role is complementary to the printed books. We hope that it will contribute to discover more about the fascinating and ever evolving field of electronic structure and materials properties goverend by interacting electrons!