Do you recommend any textbooks (or other resources) that might help an applicant become more familiar with the expected value frameworks used at OpenPhil?

I'm graduating from the University of Michigan (Ann Arbor) with an Honors History degree this year. This gave me a nonstandard amount of experience with literature reviews and research for an undergraduate student. However, I've seen that OpenPhil generally prefers its candidates to have non-humanities majors.

1) Is the latter claim true?

2) In general, how does OpenPhil rate research experience that is not in the field(s) currently being explored?