All that seems to be out there is "The Book Of THE Black Serpent" by somebody called "Opus Majus" which can be easily found by a simple Google search (always be sure to include the quotation mark so that Google looks for the exact expression, that's why adding the THE is so important). It's a small text file of 123 kB containing just an essay. It says:
[Note: This is a version of an essay published c. 1900 for initiates of the Golden Dawn Isis- Urania temple. The original essay, concerning the Qlippoth can be found in R.A.Gilbert's "The Sorcerer and His Apprentice" and Steve Savedow's "Goetic Evocation - The Magician's Workbook Volume 2". The following text was provided in Trident's edition of "Grimoirium Verum", several additions have been made and some editing has taken place -- Phil]
It doesn't mention Frederick Hockley at all (who died before the GD was founded but was made a member posthumously). All those books are in the Library and the file can be found easily, if in fact that's the one you requested. Hard to be sure without a link.
Book Requests Rule No. 2: "Give as many details as possible, including accurate title, author, publisher, edition/volume, and if possible, add an image". Makes way searching easier. No detective work required.