I first read this in 2003 after discovering the Liberal Catholic Church and mystical Christianity. Despite the crosses on the cover, the book is not specifically religious but generally spiritual, with deference and respect to all religions -- as it should be.
There is, however, a problem with this book. Not the cover, not the fonts, not the pagination, nor illustrations. The problem is that it is written SO WELL! While I just cannot believe in most of what he writes, he is articulate, measured, and sincere. I don't believe in Atlantis, Lemuria, nor Mu but he makes me want to! He is in a group of theosophical/mystical or Liberal Catholic writers from the first decades of the 20th century who ALL wrote convincing and gentle books; they were Irving Cooper, James Wedgwood, Annie Besant, Max Heindel, and Charles Leadbeater.
With regards to this book, other reviewers have gone through and detailed the the chapters. I will just say the two on the 7 Planes of Consciousness is fascinating reading. The planes, sub-planes, and repeating sub-planes (all in factors of 7) sounds as neat as the multiverse -- even though all I know of it is from Stargate Atlantis.
If you are open minded, liberal, and religiously tolerant, I suggest giving it a go. One bit of history: Henry Agard Wallace, a Secretary of Agriculture and one time VP for FDR was ordained in the Liberal Catholic Church.