ยง A = B --- A book about proofs of combinatorial closed forms

The book explains algorithms on solving closed forms for combinatorial recurrences, by means of Zeilberger's algorithm . The book is written by Zeilberger himself, and supposedy also teaches one Maple. I'd like to learn the algorithm, since it might be useful eventually for Groebner basis / loop analysis shenanigans I like to play as part of my work on compilers.