mentioned here on our Seraphim site, so out of all the books out there aside from the Bible and Book of Enoch, this one is highly recommended, especially if you want to learn about angels, demons, and the good verses evil paradigm. The book can be a challenging read in parts, and you might occasionally have to use one or two outside references to clarify certain points. Do however be sure and read it, as it will give you a great platform for researching other realms of angel based literature, as it's probably one of the most often referenced nonscriptural books on the Judeo Christian angelic world. To purchase this book simply click on the title link located above.
This great book Pseudo Dionysius The Complete Works was translated by Paul Rorem. The books focuses one of the founding blocks of Western Mysticism. It includes The Celestial Hierarchy, The Ecclesiastical Hierarchy, The Divine Names, and The Mystical Theology, all translated into modern English, so the book is very easy to read and digest. The book covers many of the topics