The seven writers who have been of the most help to me in attempting to understand Blake's poetry and thought have dramatically different perspectives on discerning the meaning in Blake's work.
Northrup Frey, Fearful Symmetry: A Study of William Blake - reveals the symbolic language of Blake within a literary context.
David V. Erdman, Blake: Prophet against Empire - explores historical and political significance of Blake's writing.
Milton O. Percival, William Blake's Circle of Destiny - relates Blake's myth to esoteric symbols, including those in the Bible, Alchemy, and Astrology.
George Wingfield Digby, William Blake: Symbol and Image - sheds light on psychological implications and symbolic meanings through commentary on The Gates of Paradise and the Arlington Tempera.
John Middleton Murry, William Blake - expounds the teachings of Blake and includes the influence of Blake's personal experience on his work.
S. Foster Damon, A Blake Dictionary: The Ideas and Symbols of William Blake - provides information on the major ideas in Blake's writing with references to locations of passages where they occur.
Kathleen Raine, Blake and Tradition - shows classical and literary sources and influences for Blake's ideas and images by placing him within traditional metaphysics.
It is because Blake thought and wrote over as broad a field of intellectual knowledge as was possible in London in the late 18th and early 19th centuries, that scholars have been able to study his work from so many points of view. These authors have immersed themselves in the whole body of Blake's work and found themselves able to focus on specific areas where their interest and expertise could shed light onto what Blake communicated. There are more books to be written, perhaps you will write one.
You are invited to read Larry Clayton's unpublished book, Ram Horn'd with Gold, focusing on Blake's spiritual development.