The personal libraries of philosophers will become the key to their biography and creativity. A book from a philosopher's personal library can tell a lot about its owner. Marginalia, dedications, and the history of the copy help reconstruct the reading circle and intellectual connections of the owner. The first part of Dmitry Furtsov's presentation will be dedicated to the personal book collections of P. S. Popov and E. V. Ilyenkov, which are stored at the Faculty of Philosophy of Lomonosov Moscow State University. The speaker will analyze the principles of forming these libraries and show why the owners' marginalia are important for the historian of philosophy. A note in the margins, an underline, or an attached document can clarify the thinker's attitude towards what they read and sometimes add to what is known from their published works. In the second part of the seminar, the discussion will focus on books from Dmitry Furtsov's personal collection. Among them are copies from the collections of brothers M. A. and F. A. Petrovsky, P. A. Florensky, M. O. Gershenzon, and Gabriel Marcel. The listeners will learn how the fate of these books unfolded and the paths they took to end up in the antique market. If you don't know where to stroll in Moscow, visit KudaGo.