The name "weird enclave of Blackmoor" was coined by Gary Gygax on the 1st of November 1973 in the introduction to the original D&D ruleset.  Blackmoor was Dave Arneson's corner of the shared D&D world we now call Oerth.  This guidebook takes into account all the material that came to be written for the Blackmoor setting over the years, but is carefully selected to remain consistent with canon Greyhawk.

In practical terms this means that many of the features, characters and events of Dave Arneson's Blackmoor are presented so as to mesh with accepted canon Greyhawk material.  In certain cases this means names or spellings are changed, but essential information remains intact.  Thus the guidebook contains detailed, system-neutral information on principal towns, history, geography and so on - with the goal being just enough information to be useful to the game master at the table.  Arneson's Blackmoor exists in multiple versions often inconsistent with each other, so educated choices were made, always with the ideal of Greyhawk compatibility in mind.  Game masters may find the extensively documented timeline particularly informative.

The book also contains a specially commissioned map of Blackmoor, consistent in outline with the map of the Flanaess, but which holds interior detail meticulously patterned on Arneson's earliest maps.  Information on additional resources and alternative ideas is included, and the whole provides a rich sourcebook for any Blackmoor-based adventure.

Lastly, this is of course a fan work, freely available per the terms of fair use.  A pdf of The Weird Enclave of Blackmoor may be downloaded here:

https://www.dropbox.com/s/4z3jgn6lsdu4jp1/The%20Weird%20Enclave%20of%20Blackmoor.pdf?dl=0

or...