Searching for books that represent bisexuality in a positive way can be tricky.
You might be interested in browsing this list (published in May 2013) of non fiction and fiction on bisexuality. The non fiction list includes a couple of collections of personal stories.
If you’re looking for teen fiction, Lee Wind maintains a list of books that include LGBTIQQ content. The listings are contained within the left-hand panel and separated into different categories, scroll down to find those that include bisexual content.
There are also a few books of note, that have been written by Australian authors: