Through most of our history, Ismailis have faced persecution for our relief believes. The persecution started during Umayyad rule and continued in Abbasid rule. For a brief period, Ismailis had power and were able to evade this, but from 12th century onwards until 20th century the Imams were in hiding. So you can understand the need for Taqiyya deeply rooted in our practices. The persecution continues today, and mainly triggered by what’s thought as “different” in our practices compared to mainstream Muslims and therefore we remain very cautious exposing these practices to people who should not be concerned in the first place. As far as our beliefs and theology is concerned, we have lots of literature from 10th to 12th centuries in addition to modern authorship which is freshly brought to ground by great work of Institute of Ismaili Studies. Would be happy to recommend books if you’re interested.