Very helpful introduction to the the general ideas behind gauge groups and the Standard Model of particle physics - Rated 
From a marketing standpoint, it's probably a pity that Dr Woit has targeted this fairly technical book at a non-technical audience, and that he has included discussion about the failure of string theory. The first section is focussed on explaining mainstream solid particle physics, and this gets fairly abstract in places, but it contains some deep physical insights about the handedness of the weak force, the problems of the Standard Model, and so on that you won't easily understand from any other book. The second half is focussed on the failure of string theory, which is very upsetting because those guys keep hyping abject speculation based on wishful thinking and "groupthink must be right" arrogance.
However, no real harm is done. You can easily skip over the quotations from Richard Feynman, Sheldon Glashow, Gerard 't Hooft and many others attacking string theory for being non-falsifiable religion, and learn about the basic concepts behind the maths of quantum field theory.
Then you can easily find more technical material as you need it. The author has some more mathematical stuff on his university home page, and the book has extensive references for further reading.
The book makes you familiar with the basic way in which gauge symmetry works and how it connects to particle interactions. A Lagrangian equation is written to describe a field, a path integral is then used to evaluate the action of that Lagrangrian. In practice the path integral, which sums over all possible ways an interaction can occur in spacetime, is expanded into a series of terms each being a power of the strength or coupling constant of the force determining the interaction. Each term in the expansion then represents one member of a set of increasingly complicated types of interaction, which can be pictorially illustrated by a Feynman diagram. Evaluating the sum of the series of terms enables you to work out reaction cross-sections, corrections to the magnetic moments of leptons, or whatever you have set up the Lagrangrian to achieve.
After reading this book, if you have also had some exposure to the kind of maths used in quantum mechanics and general relativity, you are ready to begin studying books like Ryder's "Quantum Field Theory".
Interesting but hard going - Rated 
I chose to read this after enjoying the excellent Fabric of the Cosmos by sting theorist Greene, and some interesting critiques of ST by Smolin. Unfortunately I found this book to be something of a disappointment - a lot of the background is covered in Fabric of the Cosmos, but in a far less lucid and engaging manner, and that which is new (such as gauger symmetries and Hilbert spaces) is targeted more at undergraduate and graduate physicists rather than the interested casual reader. I've given this 3 stars, because I am sure that those who really know their subject will get a good deal out of it - but for the interested lay-reader, there are in my opinion much better books out there (Smolin, Greene, Kaku).
Anti-string theorists: be aware of C.T.U. - Rated
Firstly I want to give my congratulations to Prof. Woit for his courage in publishing this book, which I presume to be the first one that dismantles superstring theory (SST), like the man in the famous tale saying that "the king is naked". I say courage taking in account the fact that a Harvard faculty member slandered critics of SSM as terrorists and claimed for an intervention of U.S. military. The title of this comment is a joke, taking into account that it is the Counter Terrorists Unity (C.T.U.) that "take care" of terrorists and not the Army. I am sure the Harvard professor doesn't consider really Prof. Woit a terrorist, but I think that his statement unveil the preponderance of the superstring theorists in the universities physics departments. Anyway I believe that "the pen is mightier then the sword".
I am a layman, so I can't say anything about SST, but I think there are some features of the theory that need to be considered in the light of Knowledge Theory.
In Arthur Jaffe's paper "Ordering the Universe: The Role of Mathematics", SIAM Review, Vol.76, No 4, October 1984, there is a diagram showing the interaction or feedback between Mathematics and Nature. That diagram may be generalised as:
THOUGHT--elaborate--> KNOWLEDGE--guides--> THOUGHT--directs--> ACTIVITY--conditions--> THOUGHT
This feedback between knowledge (or theory) and activity (or experiments) is emphasized several times in the book, but it seems that the superstring theorists ignore it; needing a spacetime of 10 dimensions to explain their theory, they are committing the same error (generally speaking) as Hipparcus, the Greek mathematician and astronomer who needed an epicycle to describe the trajectory of the planets. However, there is a difference in that the Hipparcus's method could give approximated results, while SST can't get experimental evidence. Superstring theorists seem to ignore also the fact that Kepler discovered the laws bearing his name using the data about planets compiled by the astronomer Tycho Brahe. As another example of a concept created by the mind of the physicists without any evidence and projected in the Nature as a real entity, I can cite the "ether", the medium through which the physicists thought that the electromagnetic waves propagate.
Another point I would like to focus is that some physicists are not humble persons, when they hail the SST as a "Theory of Everything". They forget that, at the end of 19th century, the physicists thought that physics was almost complete, remaining to solve only "little" problems as the ultra-violet catastrophe and the problem of the speed of light. We know the great revolution in physics that happened next to the works of Planck and of Einstein about that problems.
To conclude, I would like to refer an analogy between the development of particle physics and the evolution of mathematics. Since the birth of Quantum Mechanics until to the Standard Model the particle physics has undergone several "up-grading", each phase of the theory backing up on the previous one. This evolution is somewhat similar to the evolution of mathematics, where we see subjects of high level appearing founded on subjects of lower level.
Thinking about a career as a string-theorist? Read this first - Rated
A technically savvy but readable overview of the current state of string-theory. These are tough times for anyone contemplating a career in physics research, go with string theory and risk being out of a job when the LHC finds no evidence of super-symmetry, or don't do string theory and not get a job in the first place? Get informed, read this book and Lee Smolin's "The Trouble with Physics" then decide.
Might Just Be Right - Rated
String theory: grand unification, theory of everything or just bad science? For Woit it's devoid of predictive capability, falsifiability or experimental result - a daydream of academics all too enraptured by the `beauty' of its (possibly) self-referential mathematics. Woit feels aggrieved at string theory's domination, and therefore hindrance, of progress in particle physics - with much research funding funnelled into `string physics' at the expense of other lines of investigation. Throughout, Woit painstakingly champions quantum field theory as authentic science and the route forward.
He also takes laudable pains to demonstrate the (mostly unsung) significance of mathematicians and mathematics to the progress of all physics. This is a considerable strength of the book.
This is cold, dry, but worthwhile read, addressing deep mathematics using words (succeeding here only partially) but it is surely a refreshing counter to the stacks of popular science books peddling p-branes and other such might-just-actually-be examples of `fantasy physics' (`phantom physics'?).
All around us are people who might just be hollering the truth while most ignore them: whether noble atheists calling religious belief for the cultural fantasy it is, or possibly those such as Woit - who's one among the crowd raising his hand to declare that strings, superstrings, M-theory and p-branes are actually not wearing any clothes at all ...
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