An augmented book is an application that augments virtual 3D objects to a real book via AR technology. For augmented books, some markerless methods have been proposed so far. However, they can only recognize one page at a time. This leads to restrictions on the utilization of augmented books. In this paper, we present a novel markerless tracking method capable of recognizing and tracking multiple pages in real-time. The proposed method builds on our previous work using the generic randomized forest (GRF). The previous work finds out one page in the entire image using the GRF, whereas the proposed method detects multiple pages by dividing an image into subregions, applying the GRF to each subregion and discovering spatial locality from the GRF results.