I am reading Vol.1 of "The Quantum Theory Of Fields" by S. Weinberg. However I have come to a halt when connected Lie groups were introduced. I have solid knowledge in elementary group theory and general topology. I will now turn to studying Lie groups and algebras, and my question is:
What parts should I focus on?
What can I skip?
When is it "safe" to stop, and go back to the physics?