Just because he's reading it doesn't mean he agrees with the contents, so the photo is not evidence in itself. Also I don't think we can say for sure the photo is real. It's very easy to switch one book for another in photoshop, etc.
I've read books that I don't agree with at all but wanted to read to understand the other side of an issue. However I do think he generally would agree with such a book and so we should not let our guard down.