UPDATE - "Black Flame" study groups: now in South Africa, Canada, Denmark, US, Australia, New Zealand ...

"Black Flame" is being used in reading groups by activists in a number of countries. The book is, of course, primarily a schoalrly one, but it interfaces with the left and labour milieu in interesting ways.

There are various groups in South Africa, Canada, Denmark, US, Australia, New Zealand ...
Some examples: 
The announcement for the Hamilton, Canada, group is here.
Also groups were/ are planned by Common Cause in Toronto and Ottawa, Canada.
The book is regularly used in anarchist study circles at Wits University, Johannesburg, South Africa.
There is a reading group in Soweto, South Africa.
The "Libertarian Socialists" in Denmark's Aalborg local ran/ run a "Black Flame" reading group.
There is a discussion circle in Miami, United States, on the book.
Used by the Fantin Reading Group, Melbourne, Australia.
Used in Pittsburgh, United States.
A recent group in Seattle, United States, here

Let us know of any others!

For your  enjoyment, here is a poster produced by the "Libertarian Socialists" in Denmark for their Aalborg local's "Black Flame" reading group: