A very good way for a tourist to get the "feel" of a city is to travel around using public transportation (buses, metro, tram, train). Buying a one-day ticket for only 4 euros or a five-day ticket for 10 euros is definitely a bargain!
I read "Logicomix" graphic novel and I loved it in every aspect. The theme, the story, the graphics (I notice these words are all of greek origin) and of course the walks in Athens. Translated in 12 languages -a must read.