I've recently been researching Swift development as I have grown tired of Objective-C. However, the book I am reading (Apple's official guide) will not update to the latest version on my Mac. It updates fine on my iPhone, but it still has the same version from June that I initially downloaded on my Mac. Is there any way to update it?

I have tried deleting and re-downloading the book, and there is still no update option from the Downloads menu. I tried viewing in the iBooks Store—there is definitely a new version available. When I have iBooks check for available downloads, it says that I have downloaded all Updates and Purchases. Suggestions?