The notion of retracts was created by K. Borsuk in his doctoral dissertation [Borsuk lj published in 1931, where he studied their elementary properties. In another paper [Borsuk 3] which appeared in 1932, he introduced the important notion of absolute neighborhood retracts which includes the finite complexes as special cases. Because of this, the theory of retracts serves as the natural link connecting combinatory topology and setheoretic topology.
During the two decades since the publication of Borsuk's dissertation, the theory has been gradually generalized and developed into a somewhat mature stage. The importance of the theory, as well as the numerous interesting results, clearly indicates the need of a reference book devoted to this branch of topology. So far, there is no such book in existence. There are only two books, namely [L2J and [Ku], covering a limited portion of the theory of retracts; in fact, each of these two books devoted a chapter or so to the subject.