Srila Rupa Gosvami is described as the bhakti-rasacarya, or one who knows the essence of devotional service. His famous book Bhakti-rasamrta-sindhu is the science of devotional service, and by reading this book one can understand the meaning of devotional service. Another of his famous books is the Ujjvala-nilamani. In this book he elaborately explains the loving affairs and transcendental activities of Lord Krsna and Radharani.

From Srila Prabhupada’s purport to Cc Adi 5.203