I wholeheartedly agree with the other reviewers. I did my degree in Maths and Physics over 30 years ago and have had no professional connection with physics since. After brushing up on quantum mechanics and relativity I wanted to tackle Quantum Field Theory. I must have tried about a dozen alternative texts, many highly recommended, before I finally found Aitchison & Hey.
The authors really seem to be able to put themselves in the position of someone who is completely new to all of this. They go very easy on things like 4-vector notation, often writing out equations in more familiar vector calculus form, especially at the start of the book, until the reader feels more comfortable with covariant notation.
The appendices are particularly helpful and fall into two categories: those which summarise what you should already know, and those that teach the basics of techniques that might be unfamiliar. All the appendices are useful but I found those on the Dirac delta function, contour integration (they teach you what you need to know for this book in only six pages!) and Greens functions particularly so. Thanks to the appendices, I found the book to be almost entirely self contained.
However, a warning: QFT is probably one of the most difficult subjects that anyone can try to master on their own. Even A&H I found to be quite challenging in places. It has taken me nearly a year and I still haven't quite got to the end of volume one, with one chapter alone taking me nearly three months to complete.
It is often said that no one book can teach you QFT. That may be true, but A&H have come, by far, the closest of the many volumes that I have tried.