I was always interested in learning QFT but none of the available books (P&S, Srednicki, Zee's Nutshell) could offer me a clear understanding of the logic and reasoning behind QFT's esoteric formalism. That all changed after taking on Matthew Schwartz's book. There is so much to tell about this marvelous book, therefore I have thematically split my review into 5 sections below.
Style of presentation: This is by far the most *congenial* (not for a lack of adjective) physics book I have taken on so far! The book adopts a refreshingly friendly and colloquial writing style (much like a tutor), calling out the big picture and stressing the important points in every discussion. It not only explains how the theory should work, but also how it should not, by pointing out the possible naive interpretations that a novice might make; Along the same line, the author keeps comparing the new topics with previous ones, in a non-repetitive way, each time shedding more light from a different angle, which helps bolster the core ideas in the reader's mind without overwhelming him/her, allowing the reader to make some profound conceptual connections.
Intuition and depth: This is the most intuitive QFT book I have seen. Ideas that previously were merely mathematical equations became commonsense after being exposed to this book. Matthew Schwartz transcends the math beyond what is offered by the classic references in the field by adding his well-worded intuition, targeted at a graduate student. Just as a few examples from the first quarter of the book, the meanings of the commutation relations between the fields and their derivatives are beautifully tied to causality, the LSZ formula is demystified by making it responsible for generating the initial and final states, the essence of QFT interactions is concisely (and yet fully) presented (in only a few pages) through the Lagrangian derivation of the Feynman rules, prior to presenting the messier, yet more systematic Hamiltonian formulation, the guage-invariance and Ward identity are discussed in great depth through various illustrative examples, the discussion of various representations of the Lorentz and Poincare groups are quite unique, thanks to providing topological pictures and realistic numerical examples after building the math machinery, etc.
Breadth: The multitude of topics covered is extensive, ranging from QFT and QED, to a complete treatment of the Standard Model, QCD and advanced topics such as background fields, heavy-quark physics, jets and effective theory. Moreover, each idea is presented/formulated through various approaches/methods, e.g. Feynman rules are derived in space mode and momentum mode using both Lagrangian and Hamiltonian approaches.
Level, rigor, and notation: Without a doubt, this book (and frankly the whole subject) is intended to be taken up by a physics graduate student, although a talented senior undergraduate should also find the book useful. As for the mathematical rigor, I would describe it as "just enough", for a physics book. As far as notation, the author has been very careful not to confuse the reader by using excessive/abstruse notations; the author uses the modern conventions (first print is in 2014) and all the notations are clarified upon introduction.
Necessary background: In order to really appreciate the book the reader should have a solid background in Quantum mechanics (Lagrangian and Hamiltonian formulations, spin, scattering, etc) and know the basics of Special theory of relativity, Electrodynamics, matrix algebra, multivariable calculus, and Complex integrals.
As a final note, I should mention that the book has its own website, with a newly launched Forum section, where the author graciously answers readers' questions.
Overall I really enjoy reading this book and highly recommend it.