Recommended books:

An Introduction to Quantum Field Theory by Michael E. Peskin, Dan V. Schroeder.

Quantum Field Theory by Claude Itzykson, Jean-Bernard Zuber

The Quantum Theory of Fields (3 volumes) by Steven Weinberg

Books:

Quantum Field Theory in a Nutshell by Anthony Zee

Quantum Field Theory by F. Mandl and G. Shaw

Quantum Field Theory by Mark Srednicki

Relativistic Quantum Mechanics by James D. Bjorken & Sidney D. Drell

Quantum Field Theory by Lewis H. Ryder

Aspects of Symmetry by S. Coleman

Gauge Fields and Strings by A. Polyakov

Recommended on-line resources:

Lectures on Quantum Field Theory by David Tong (a pedagogical introductory course)

Quantum Field Theory by Mark Srednicki (the draft of the book)

On-line resources:

QFT Lecture Notes by Michael Luke (based on Sidney Coleman's notes)

Introduction to Relativistic Quantum Fields by Jan Smit (lecture notes)

Quantum Field Theory by Pierre Van Baal (lecture notes)

General Field Theory by Eduardo Fradkin (lecture notes)

Quantum Field Theory by Bernard de Wit (lectures notes)

Fields by Warren Siegel (a textbook)

Another type of on-line resources:

Hans Bethe lectures QFT (video)

Peter Higgs "My life as a boson" (video)