Confused about DJVU files and converting to LRF
I'm trying to convert a book at the Internet Archive into a LRF file for my Sony 505. The text is available in TXT, DJVU and PDF formats. The TXT file isn't pure text, but contains some HTML. The name of the TXT file also has the letter sequence DJVU, suggesting that the format is related to the DJVU format. Meanwhile, the actual DJVU file is about 20x the size of the TXT file (about 20M) and the PDF file is around 50Megs.
Which is the best file format for converting to LRF? What is the best program for converting one of these formats to compact LRF?