This book presents 18 articles by prominent mathematicians, dedicated to the memory of Alexander Reznikov (1960-2003), a brilliant highly original mathematician with broad mathematical interests. In addition it contains an influential, so far unpublished manuscript of Reznikov of book length. The research articles broadly reflect the range of Reznikov's own interests in geometry, group and number theory, functional analysis, dynamical systems and topology. In addition, there are surveys "Geometrization of probability", "Kleinian groups in higher dimensions", "(C,F)-construction of funny rank-one actions for locally compact groups", and some articles centering on Reznikov as a person.