Yes! Books are in the add-ons section. The limit is one extra book -- your shipping won't change at all by adding a second book, so this is a great option in particular for backers outside of the US who can team up with someone to order their books together.
I know the shipping is horrible, but this way, if you have a friend who would also like a copy, you can get both books and split the shipping by simply adding an extra $25 USD onto your pledge. I will be able to confirm add-ons in the backer report when the campaign is successful.
If you are an LCS owner, you can pledge on the retail tier for 5 books!