Format .lrf is primary format for BBeB, it means Broad Band eBooks. They are created by Sony and Canon companies. It is also created for Sony Librié. Moreover it supports other e-books from Sony. This is unecrypted file formats, their base is built on XML, but it´s not open file format, which is different from .lrs format, which is its ancestor. Its successor is .lrx format, which supports encryption. To get files in this file format, you only need to reformat .html or .pdf files and they can be obtained almost everywhere.
Because Sony developed this format, it is clear that this company created its own program to open files in this format. It is called Sony Reader and it´s available for Windows and Mac OS, but it´s only available in USA and Canada. Next application which is not limited to USA or Canada is Calibre. This program can be used on Windows, Mac OS and even on Linux, which makes him the most comfortable program for reading files saved in this file format.