I think The Gay Science, Beyond Good and Evil, and A Genealogy of Morality are very readable and thought-provoking without going into esoteric ism or experimental style like Thus Spake Zarathustra. I prefer the Kaufman translations, but I understand there are many new, possibly better translations available now. Translation can make-or-break Nietzsche - he was one of the best German prose writers and makes use of a lot of wordplay and neologisms.

The first quote was from Gay Science - I grabbed the second of Wikipedia, but I was sure it, or something to the same effect, was also in Gay Science. I don't have a searchable copy of my favorite translation, unfortunately, but Nietzsche talks a lot of psychology in Gay Science.