I've never heard of giving applicants material before the interview. More commonly, I think companies give new hires (especially interns) a book or some material to read before their start date, but usually the investment comes after the decision.

Did the book shape the interview? Like if I didn't read it, I'd have a hard time? Or maybe even if I nailed the book, but didn't know anything else, that'd be bad?

The books did not shape the interviews, and we were careful to tell candidates that they shouldn't treat them as homework, and they could probably do just fine without reading them at all.

What are the other books, if you don't mind me asking?

I think 'tptacek wrote in some other thread about WAAH and Cryptography Engineering being two of the others.

WAHH and The Art Of Software Security Assessment (TAOSSA) were the other two. We didn't grill candidates on crypto or have work-sample tests that involved crypto. Sadly: you'd be discarding 95% of the candidate pool, and particularly and paradoxically the experienced candidate pool, if you screened for crypto ability. The software security field is just awful at crypto.

Thank you, much appreciated.