.BOOK file format is associated with Adobe FrameMaker. This application is used to make large and complex documents.

The application allows the user to write in number of languages along with extensive support of number of image file formats. All the information related to the characters of the language used and image file sizes and placements is stored in a single writable file which is given the extension of BOOK. The main focus while compiling the file is on the structure of the document. As this file format is used to store a large amount of data, the information related to their structure and relative place is also saved while compiling the file.