Two books that I think would be especially worthwhile are Pirkei Avot, or "The Ethics of our Fathers," which is a compilation of watchwords from a number of rabbis during the early talmudic age (it's a very short book), and To Be a Jew: Guide to Jewish Observance in Contemporary Life by the late Hayim Halevy Donin.
Thank you. I will add those to my list.