Shams al-Ma'arif al-Kubra (The Great Sun of Knowledge) is not a singular, easily defined book. Rather, it is a compilation of esoteric knowledge covering:

in English is surprisingly difficult. The original text is over a thousand pages long and written in dense, medieval Arabic.

Elias remembered the stories. Al-Buni had warned that the book was a living entity. A book of light. If you read it without the proper spiritual protection, the "Sun" would not illuminate you; it would burn you to ash.