The Works of Plutarch
Plutarch was born in 46 C.E. in Chaeronea, in Boeotia, Greece,
and died about 119-127.
He was one of the two priests of Apollo at the Oracle of Delphi.
His skills as a writer and speaker brought him
fame in the first century Roman Empire.
Often cited in other books at this site, of interest are
the extensive passages where he discusses
puzzling points about ancient Paganism.
In spite of his priestly background, Plutarch was a bit of
a free thinker, and loved to speculate multiple explanations
for natural and cultural phenomena.
As such, he is one of the predecessors of modern social science.
Plutarch's Morals: Theosophical Essays
tr. by Charles William King 
Six essays by Plutarch, rich with details of ancient mythology and natural philosophy.
Includes the following essays from the Moralia
On Isis and Osiris
On the Cessation of Oracles
On the Pythian Responses
On the E at Delphi
On the Apparent Face in the Orb of the Moon
The Roman and Greek Questions
of Plutarch, tr. by Frank Cole Babbitt 
A treasure trove of classical pagan lore.
Elsewhere at this site
Legends of the Gods: The Egyptian Texts
Includes the De Iside et Osiride of Plutarch
by E. A. Wallis Budge