Which sort of Cichlids?
C/A:
"The Guide to Owning Central American Cichlids," Dick Stratton
"Cichlids of North and Central America," Donald Conkel
Oscars:
"The Guide to Owning Oscars," Stratton
"Oscars," Neal Pronek
Tanganyikans:
"The Tanganyikan Cichlid Aquarium," Georg Zurlo
"Lake Tanganyikan Cichlids," Mark Phillip Smith
Malawians:
"Lake Malawi Cichlids," Mark Phillip Smith
Both Rift Lakes:
"Cichlids from Lakes Malawi and Tanganyika," Sabine Melke *EXCELLENT!!!*
Cichlids, in general:
"The Cichlid: An Owner's Guide to a Happy Healthy Fish," Mary Ellen Sweeney
"Tetra's Popular Guide to Tropical Cichlids," Paul Loiselle
"Cichlids," Zurlo
Note that I have only suggested books which I personally own, because I cannot, in good conscience, suggest ones which I haven't bought or would never buy.