This is a novel of Atlantis, written as a channeled message from
a disembodied sage named 'Selestor.'
Selestor recounts the history of Atlantis, from its rise to its destruction,
thousands of years ago.
The author does not use the usual framing story as many of these books do.
Instead she dives right in, with the implication that she sees what
has been written here as the literal truth.
The book is written in an affected, slightly archaic
style reminiscent of (but certainly not in the same league as),
Robert E. Howard, Lord Dunsany or
E.R. Eddison.
However, this makes the book much more readable than
other occult novels such as
A Dweller on Two Planets,
or Unveiled Mysteries.
Even when Selestor is going on about mineralogy, it still sounds a bit
like an oriental opium dream.
Selestor's Atlanteans have advanced technology, including some kind of
super-telescope which allows them to observe and even hear battles on the
planet Mars.
Selestor provides much detail about the culture and history of the Atlanteans,
including their laws, industries, and science.
They are somehow contemporaries of Vikings and Mayans
(or their prehistoric predecessors).
They even engage in a spectacular naval battle with the Northmen,
similar to an episode in Cutcliffe Hyne's
The Lost Continent.
The author, Clara Iza von Ravn, is a bit of a mystery, at least
on the Internet.
She is often listed in bibliographies as one 'Mrs. Tibbets.'
She appears to be an American citizen living on the west coast.
So it is likely that the 'Baroness' title she is given on the back cover
blurb is probably an affectation.
I can establish that she was born in 1870 and died in 1942,
and wrote one other book with an occult theme,
The Scribe of a Soul
(Seattle, Washington: Denny-Coryell Company) in 1901.