MTT – Multi-Table Tournament.
Hijack – The player who acts preflop before the cutoff, who acts before the button (or dealer).
GTO – Game theory optimal
Nit – A player who is too tight for their own good.
Lowjack – Not very common to use, but acts preflop before the hijack.
You could easily google any other terms you might not understand, and as for poker books, I don’t have any first-hand experience but The Mental Game of Poker is a typical first choice from what I’ve heard.
Good luck at the tables!