These books are free for you to browse.
Freemasonry, its symbolism, religious nature, and law of perfection
The Mysteries of Freemasonry by Captain William Morgan (yes, that Morgan!)
A Lexicon of Freemasonry by Albert Mackey
Morals and Dogma of the Ancient and Accepted Scottish Rite by Albert Pike
Freemasonry from the Great Pyramid of Ancient Times
Encyclopedia of Freemasonry and its Kindred Sciences by Albert Mackey