A couple of books that I have recently read that I would highly recommend are the following:
Islam in the African American Experience by Richard Brent Turner
This is a book by a prof at Xavier University. It is probably the best book that I have read on the development of and African American Islamic tradition. He begins with Islam in West Africa analyzing how after its introduction by Berbers from North Africa, it was adapted and existed along side of African traditional religions for centuries. It was this blended tradition that made it to America with 7-8% of enslaved Africans being Muslim. This population is interesting because it included scholars and dignitaries who spoke and read Arabic and who retained their religious practice during slavery.
Other highlights - Turner sheds light on the AA Islamic community and their early connections to Pan-Africanism and Black Nationalism. There is the incredible influence in the AA Islamic community from Indian Islam through Ahmadis and the Ahmadiyya Movement.
Santeria from Africa to the New World: The Dead Sell Memories by George Brandon
This is a nice summary of the development of Santeria. His principle argument also deconstructs the notion of syncretism and the scholarly obsession which purity of traditions. The other interesting thing for me about the work is that he makes a strong case for Santeria being an urban phenomenon and that its introduction in the US was the catalyst for many AA's to seek to return to Orisha religions.
Spiritual Churches of New Orleans: Origins, Beliefs, and Rituals of an African American Religion by Claude F. Jacobs and Andrew J. Kaslow
This book deals with the Spirit Church movement, one of the most understudied AA religious traditions. It is a thaumaturgical (magic and miracles) tradition. Again, it has been seen in negative light by more orthodox Xians for its "syncretism" of African, European, and indigenous practices that emphasize healing, spirit possession, etc. These churches are particularly strong with respect to the involvement of women. One of the founders is Mother Leafy Anderson who channeled spirit of the Native American rebellion leader Black Hawk.