I would first like to apologize for posting a question similar to others previously posted.
I've already had an undergraduate course in logic but we did not use a standard text. Rather, we discussed the main ideas of propositional logic, predicate logic, and a bit on undecidability; though nothing too deep. Consequently, I'm seeking a text to advance my understanding via self-studies.
I've skimmed through some of the logic texts by Enderton, Ebbinghaus Flum Thomas, Wolfgang, and Shoenfield at my school's library and they all seem manageable.
Personally, I'm leaning towards Shoenfield or EFT.
My concerns/questions are:
1.) Are the notations of these old texts severely outdated?
2.) Do they cover distinct systems?
3.) Are there any conventions that are simply just not used anymore with the older texts?
4.) Would these (any) make a good book for an intermediate level? Are there any other good books you would recommend instead?
Edit: I should mention that my undergraduate course covered very little compared to any of the texts. That is, we skimmed over model theory and we took some things for granted (some of which were spontaneous (ex: Skolem's Theorem)) since set theory was not required.