Stereograph of the Pyramids and Sphinx  (Public Domain Image)
The House of the Hidden Places
by W. Marsham Adams
There were many speculative attempts to explain the internal architecture of the Great Pyramid of Giza in the 19th century. Most of them were composed with an eye to Christian dispensational prophecies. Adams, on the other hand, thought that the blueprint for the Great Pyramid was the recently translated Egyptian Book of the Dead, a journey of the soul through the afterlife. He viewed this as an allegory of initiation, a precursor of Masonic rituals. Adams was dismissive of the 'pyramidologists.'
When this book was initially published, it was taken seriously by many scholars and esoteric researchers. However, the lack of scholarly apparatus was a stumbling block for many. In addition, the Great Pyramid was constructed about 2500 BCE, and first versions of the Book of the Dead date to about 1500 BCE: a gap of nearly a thousand years. So the Great Pyramid could not possibly be based on the Book of the Dead. Although Adams drops hints about high-level Masonic themes in the Pyramid and Book of the Dead, he was not a member of any Masonic group. On the balance, some of Adams' ideas were ahead of his time, particularly his theory that the Egyptians were African in origin, not Asian, as most believed at the time. G.R.S. Mead, although critical of Adams' methodology, thought that there was a kernel of truth in his thesis.
Not much is known about Adams' biography, other than that he described himself as a fellow of New College, Oxford. It is unknown when he died. This makes determining its copyright status difficult in countries which use the date of decease of the author as a criteria for copyright terms. However, it was probably over 70 years ago, since he was born in 1837. Unless he lived to over 100, it is probably safe to say that this book is public domain in the vast majority of countries. He followed this book up later with The Book of the Master in 1898, which was more speculation about Egyptian religion, and also wrote six other books on unrelated topics.