The books by Bratteli and Robinson (the link is for volume 1 that is more on the abstract theory of C* and W* algebras, there is also volume 2 that has physical applications) are a standard reference on C*-algebraic methods in physics, even if the applications they develop are mostly in statistical mechanics. Nonetheless, the concepts introduced have important applications also in relativstic quantum field theories.

The book is not introductory, and a bit heavy to read, but contains many very interesting results.

Also local quantum physics by Rudolf Haag is a standard reference, written by the pioneer of algebraic QFT (that introduces, e.g., to the concept of nets of algebras of local observables).