From its own cover,

It is written by experimental physicists and aimed to provide the interested amateur with a bridge from undergraduate physics to quantum field theory. The imagined reader is a gifted amateur possessing a curious and adaptable mind looking to be told an entertaining and intellectually stimulating story, but who will not feel patronized if a few mathematical niceties are spelled out in detail.

This might sound pretty casual, but it gets into all the math of it, with an aim at practical use.

The book “Quantum field theory for the gifted amateur” is really good. It’s helped me understand quantum fields a lot better, and I work with quantum mechanics every day.