The Lost Keys of Freemasonry: Now Available!
This is the second piece of literature ever crafted by Manly P Hall. It is a very good guide to the basic premise of Freemasonry- the symbolic tale of Hiram Abiff forms the basic symbolic core of its tenets, along with some other themes explored herein. It is notable that Hall was not a Mason at the time of writing this work but was apparently applauded by the order anyways, despite barely being an adult.
There is an interpretation of the fabled Emerald Tablet of Hermes here that is notable as well.