I tried to use:

/give @p written_book 1 0 {pages:["{text:\"Hi\"}"]}

I also tried:

/give @p written_book 1 0 {pages:["[{text:\"Hi\"}]"]}

The book it gives me says Invalid book tag.

This really sucks, because we've been having JSON related issues since 15w31a, and I really want it to work for a thing I'm working on for 1.9.