I have two recommendations you might find useful. The first is QED, a series of lectures by Richard Feynman. This text covers the qualitative nature of the perturbation theory used for quantum electrodynamics. The second is Quantum Field Theory for the Gifted Amateur by Lancaster and Blundell. It's nicely written and accessible at the advanced undergrad level, building up QFT from the basics.

Caveat-- I work in astronomy but have a PhD in physics and have taken graduate QFT.