I'd say reading having a read of Bertrand Russell's 'A history of Western Philosophy' is a solid start. [0]

You can branch out from there, based on who appeals to you personally.

[0] https://www.amazon.com/History-Western-Philosophy-Bertrand-R...

A really brief introduction to almost all of western philosophy (a big section on the major greek philosophers) (and its not a slog at all) http://www.amazon.com/History-Western-Philosophy-Bertrand-Ru...

I would recommend it to anyone who wants to trace the thoughts of the Greeks forward to WW2 era-ish, thoroughly enjoyable read.

ZAMM is a terrible introduction to philosophy. Fun story, bullshit philosophy. I'm not actually sure whether the author believes this "metaphysics of quality" stuff or whether he's just putting it into the mouth of the character.

If you want to learn about philosophy, start with Russell:

http://www.amazon.com/History-Western-Philosophy-Bertrand-Ru...

Bertrand Russell - The History of Western Philosophy:

http://www.amazon.com/History-Western-Philosophy-Bertrand-Ru...