So far, it's an interesting, unique view of a dynamic European secret tradition. I don't want to say "witchraft" because this easily gets confused with Gardnerian wicca, speaking of which, one of the most humorous things about Cochrane's letters is how he loves to loath the wiccans! Cochrane believes his tradition, and he claims to be one of the last survivors if a hereditary witch clan, is more affected by Persian magic in the era of the Crusades than simple "peasant" nature worship. Humm...at least he has lots of cute anecdotes about his kitties.
Another compendium of letters by Roy Bowers, aka Robert Cochrane, outlining his religious philosophy that inspired the traditions Tribe of Tubal Cain, 1734, and the Roebuck. I'm not convinced it's any type of tradition passed on unbroken, but rather a gifted individual able to link into an occult current who was able to revive older techniques that had died out.