Hi. I'm studying (introduction to) QFT, and I'm really lost. If possible, I'd like a pointer to a good textbook on the subject. I'll give an example of my confusion with a question: I think I've understood phi(x) as a classical scalar field, what it is and how to use it in a lagngian for classical field theory. I'm totally lost on how it works in QFT. My understanding is that it is now an operator on the hilbert space of states, like X or P were in quantum mechanics. Actually, it is a whole group of operators - each phi(x) give a different operator for a different x In quantum mechanics, the way the X operator worked, it was an observable, with eigenvectors being definite states and eigen values being the values of the observable.... What's going on with phi(x)? What is this operator? Why am I using it like I used the classical scalar field phi(x)? Before even getting into any of the ugly calculations and normalizations, I'm trying to understand the basic "rules and players". What are the different operators and functions, what do they depend on, what do their values means, how are they dynamical... I'm very mathematically minded, so I'm hoping to find a book in that style. As an example - I really like Sean Carroll's General Relativity textbook.