Book excerpt: Beginning with the structure, types, functions, and gene organization of antibodies, the book aims to shine a detailed light on the monoclonal antibodies (often referred to as mAbs) that have revolutionized the fields of therapeutics and diagnostics. The book describes the different ways of generating chimeric, humanized, and fully human monoclonal antibodies, emphasizing phage display, hybridoma, and rDNA technology. In addition, the book focuses on the various recombinant antibody formats in detail: Drug conjugates: Antibody-drug conjugates (ADCs), Immunotoxins (Recombinant, Humanized and Fully Human) and Antibody-antibiotic conjugate (AAC) Bispecific antibodies: scFv based (BiTE, DARTs and TandAbs) and Full-length IgG based Abzymes and Antibody-directed enzyme prodrug therapy (ADEPT) Fc-fusion proteins Single-domain antibodies (VHH and IgNAR sdAb) The book discusses the various therapeutic applications of monoclonal antibodies, along with the immunogenicity issues. The book also covers the modes of administration and side effects of monoclonal antibodies, along with the challenges and issues faced while developing a monoclonal antibody into a therapeutic agent. Modifications introduced by the researchers to decrease the immunogenicity issues and increase the efficacy of therapeutic mAbs are also described. The book is an invaluable resource for researchers and students in biology and medicine, biotechnology, immunology, genetics, molecular biology, and anyone interested in antibody engineering.