Morals and Dogma
by Albert Pike - 1871
This book is a series of 'lectures' on the esoteric roots of Freemasonry, specifically the 32 Degrees of the Scottish Rite.
I was given this book when I was initiated into the Scottish Rite. It was my constant companion as I went through the 32 degrees. Over time, I have read and re-read this book numerous times, wearing the binding off my first edition. The book can be a difficult read, but I find it to be the most comprehensive writing on Esoteric Philosophy in existence.