Transitioning seamlessly from the real world into the digital world through the mixed reality continuum remains challenging. This paper investigates transitional design principles across the MR spectrum, anchored by a review of “The MagicBook”, a pioneering work that introduced the concept of transitional interfaces to the HCI community. Employing a forward-backward method, we reviewed 309 publications to understand the landscape of MR transitions. Our analysis outlines four distinct transition types within MR environments, offering a novel classification scheme. From this literature corpus, we identify four categories, setting a foundation for UX evaluation of transitional interfaces.