The problem of course is that there really aren't books on advanced Wicca, but there are many books that will help deepen your understanding of the religion of Wicca and how the beliefs and practices of Wicca are important to adhere to. Here are some books that I'd suggest:
"Castings" by Ivo Dominguez
"A Study of Witchcraft" by Deborah Lipp
"Devoted to You" by Judy Harrow
"The Elements of Ritual" by Deborah Lipp
"Path Through the Labyrinth" by Marian Green
"The Other Side of Virtue" by Brendan Myers
"Covensense" by Patricia Crowther
"Wicca Covens" by Judy Harrow
"Gerald Gardner and the Cauldron of Inspiration" by Phillip Heselton
"Witch Father" by Phillip Heselton
"Religion Without Beliefs" by Fred Lamond
"Spiritual Mentoring" by Judy Harrow
"The Pagan Book of Living and Dying" by Starhawk and M. Macha Nightmare
"Kissing the Limitless: Deep Magic and the Great Work of Transforming Yourself and the World" by T. Thorn Coyle
Theology:
"Pagan Theology; Paganism as a World Religion" by Michael York
"A World Full of Gods: An Inquiry into Polytheism" by John Michael Greer
"The Deities Are Many: A Polytheistic Theology" by Jordan D. Paper
Ethics:
"When, Why...If" by Robin Wood
"An Ye Harm None: Magical Morality and Modern Ethics" by Shelley Rabinovitch & Meredith MacDonald
"Living with Honour" by Emma Restall Orr
"The Other Side of Virtue" by Brendan Myers
"Ethics for the New Millennium" by the Dalai Lama
Living Mindfully:
"The Miracle of Mindfulness" by Thich Nhat Hanh
"Living the Mindful Life" by Charles Tart
History:
"Pagan Religions of the Ancient British Isles" by Ronald Hutton
"Stations of the Sun" by Ronald Hutton
"Triumph of the Moon" by Ronald Hutton
Personal Transformation:
"Make Magic of Your Life: Passion, Purpose, and the Power of Desire" by T. Thorn Coyle
Magick:
"Modern Magick" by Donald Michael Kraig
"The Veil's Edge" by Willow Polson
"Spells and How They Work" by Janet and Stewart Farrar