We review recent progress in the study of a famous quantum integrable system. Its limits and particular cases such as Calogero – Sutherland, Toda systems are well known and are studied for many years. Analytical continuation of Ruijsenaars system leads to Macdonald operators and the theory of Macdonald symmetric polynomials. Ruijsenaars hyperbolic system itself can be also explicitly solved by the methods which differ much from commonly used algebraic machinery and finally leads to a distinguished multivariable generalization of Fourier transform.