Is it just called Alamut?: https://www.amazon.com/Alamut-Vladimir-Bartol/dp/1556436815

For the Ismaili side, I'd recommend Assassins Legends and The Eagle's Nest (pretty much anything by Farhad Daftary is a good read). For the non-Ismaili side, there's lots of stuff but I'd actually recommend Alamut. It's a novel, but Bartol spent a decade researching the subject and the result is a really compelling look into how this could happen.

In context, you have to remember that Ismailis were stuck between Seljuks and Crusaders (both of which hated them) and no longer had a serviceable army to protect. So these lone assassins probably sounded like a great idea, regardless of what the leaders said.

That's it for Assassin Stuff. The rest is on the blind faith question...

One of the things that drew me back to Ismailism is that Hazar Imam has always encouraged us to think critically, even about his faramin (it's like page 2 of Precious Gems). Rationality, critical thinking, and the application of a personal intellect are (and always have been) tenets of Ismailism: followers of Jafar alSadiq were known as the "People of the Truth"; Hassan Sabbah (founder of the Assassins) famously asserted that "nothing is true"; and for most (if not all) Ismaili philosophers, the the soul is the intellect. That's how I keep my faith: "I think therefore I am Ismaili", "seeking knowledge is an act of worship", etc.

However, there's this subset of Ismailis that take the Pir's (or worse, the Quran's) words at face value; there are still Ismailis that deify the Imam. Some of the stories in this sub criticise that belief-set, and rightfully so: it's stupid. But I ain't about that life, y'all ain't about that life, and (importantly) Hazar Imam ain't about that life, at least not on the surface. There is the argument that he's encouraging these beliefs by not countering-them outright (like he hasn't encouraged dasond, but he also hasn't stopped it, y'know). But when you're trying to keep the faith of 20 million people, certain secessions have to be made.

The question I'd really like an answer to is: out of everything that Hazar Imam is doing, how much is meant to carry on the Tariqa (knowledge leads to divinity, etc) and how much is just to appease his followers? Because he needs us as much as we need him.

I hope that answers your question. If not, I totally don't mind getting into specifics.