Virginia Comolli, Boko Haram: Nigeria’s Islamist Insurgency is reviewed at African Arguments. Along with Mike Smith’s Boko Haram: Inside Nigeria’s Unholy War, these look to be the key English books on the group.

My bibliography of articles (last updated in 2014) can be found here; and my own essay “The geopolitics of Boko Haram and Nigeria’s ‘war on terror’” here.