That book is good but a little outdated. For current penn testing I HIGHLY recomend this book by Andrew whitaker. He is a true Guru of the ethical hacking field.
Plus if you are a noob to linux what you should be reading is this
http://www.oreillynet.com/linux/cmd/
http://www.linuxdevcenter.com/linux/cmd/
http://bashscripts.org/



