I was reading earlier about the Ikwhan al-Safa and the Encylopedia ascribed to them and it seems like an extremely interesting and fascinating document. However, I am still somewhat confused about the group itself. It seems like a lot of arguments are made about if this was a specifically Shiite or sectarian group but the materials that are easily visible at first glance don't seem to say a lot beyond the Encyclopedia ascribed to them. Are there references to the Ikhwan in other texts, or citations to the Encyclopedia that provide additional information on its author(s)?
(apologies if I have asked this question before, I don't always have the best memory.
I'm a little late to answering this, but Farhad Daftary writes briefly about them in The Isma'ilis Their History and Doctrines and names Abu Sulayman Muhammad bin Ma'shar al-Busti, Abdul Hasan A'li bin Harun al-Zanjani, Abu Ahmad al-Nahrajuri and al-A'wfi as members although he only explores the group for a few pages.
The actual beliefs of the group are explored much more thoroughly in Godefroid de Callatay's Ikhwan al-Safa' A Brotherhood of Idealists on the Fringe of Orthodox Islam.
The problem you're running into is that the group was deliberately secretive as some of the views they put forward could be seen as heretical by Muslim (or other Muslim depending on how you view the religion of the Ikhwan al-Safa) groups in the area. It is generally, although not uniformally believed that they were ultimately loyal to the Fatimid Caliphs and a lot of work they seemed to be doing was trying to mend the Fatimid Qarmatian schism. However when a group tries to reconcile two other groups that aren't interested in reconciliation you end up with three distinct groups.
Sources:
Farhad Daftary, The Isma'ilis Their History and Doctrines, Cambridge: Cambridge University Press, 1990
Godefroid de Callatay, Ikhwan al-Safa' A Brotherhood of Idealists on the Fringe of Orthodox Islam, One World Publications, 2006