This is very simply an extraordinary book. Some of Nietzsche's best writings are included in this book, all translated by Walter Kaufmann - Kaufmann being, of course, one of the greatest scholars of German literature (and Nietzsche in particular) of the twentieth century.
The translation seemed very good to me, and I've enjoyed Kaufmann's translations before - particularly his book "Goethe's Faust" is one of the best poetic translations I've ever read.
This collection of Nietzsche's writings are completely enjoyable, the life and muscle only brings grins to the face of those who dare to experience it. Especially good language in the translation is something to note.
Every book, or snippet in this chronicle of sorts is indispensable, but THE BOT is really a great place to embark. The way that all the books tackle/attack Christianity and problematic ideals of morality - and the traps that mankind finds itself within these self made pits - makes Nietzsche something of a superman even by todays standards.. but just think, he was doing this way back in the mid 1800s.
This is where everyone should start to learn and enjoy the wonderful writings of what could really be considered one of the last great philosophical thinkers... with only exception might be B. Russell.