My grandmother is a very intelligent lady, but she's also very religious (which, yes, sounds contradicting). She's always been "defensive" when I make comments about how her European-looking Jesus paintings are inaccurate, or anything regarding anything of that sort.
She's an avid reader and reads about most any topic. She often asks me to get her more information about these things, so I'd like to give her some good books with an unbiased point of view, perhaps not just about Jesus, but also about "demythifying" various points from the Bible with concrete historical facts. Again, she's open minded but I don't think she'd really take anything too seriously if it were somehow literally attacking her religious views, rather than stating it in a neutral way.
Any recommendations? Thanks in advance!
No, there aren't, because there's a flaw in your reasoning to get to this question.
You can love the Bible, or leave it, or critically analyse it, or re-write it to fit your own view of what happened, but it's still a set of documents written in a particular context that needs to be read and understood in the context. That's just part of the discipline of reading historical literature.
So what happens if I, say, write a biography of Jesus and take out everything I think is unhistorical. Say I remove everything that seems miraculous or far-fetched. What's left? What's left is not unbiased, it's a 20th century re-telling of the gospels that tells you more about what I think than anything about the historical Jesus. It's really a work of historical fiction.
This is in fact the market of books you're asking about - historical fiction. There is no unbiased position. There is no 'neutrality' here. In my view, the value of 'objectivity' means owning up to your own biases, and let me be clear my bias is against using 'objectivity' as a criterion to privilege certain viewpoints.
I would say, if you want your grandmother to think intelligently about the Bible, get her books that engage critically and intelligently with the Bible. To me it sounds like you want books that will persuade her of the Bible's unreliability, under an appearance of objectivity. Isn't that just projecting your own view onto her.
You may be interested in the FAQ section on Did Jesus Exist? and, to some extent, the section on Reza Aslan's "Zealot: The Life and Times of Jesus of Nazareth".
Did Jesus exist? by Bart Ehrman might be an interesting book for her. It discusses what Jesus might have been like from a historical rather than a religious point of view. Bart Ehrman is an agnostic, not a Christian.
How does this sub feel about Elaine Pagels? Her credentials seem good (to me), and the books of hers that I've read, especially The Gnostic Gospels and The Origin of Satan, offered an interesting perspective. I'd be interested in how credible the larger historical community considers her.
I thought Pagels might be especially interesting to OP because she identifies as Christian, at least in some form:
Because the language and the characters of the Bible are so familiar to her, Pagels adds, she identifies as Christian -- "but I wouldn’t say I identify only with that."
http://alumni.stanford.edu/get/page/magazine/article/?article_id=36367
so while she approaches the subject as a scholar, she's not antagonistic to religious belief.