Hi ... here's a quick one that may be useful now or in the future ... It has to do with the opening of ".DjVu files". As you know, sometimes you come across files ... e. g. ... .CHM, .DJVU, .LIT, .PDB .MOBI files, etc. that are hard to open. I downed a cool Math file in the djvu format and found a link which led me to an acceptable program to use ... The link is ...
http://www.interrupt19.com/2008/10/02/how-to-read-e-books-in-os-x-chm-pdf-djvu-lit-pdb-and-mobi-files/
It provides info. on more files types than .djvu & all ... Check them out - btw, I checked at MacUpDate and found a program called MacDjView which must be put out by the same people, but is quite limited in scope ... all you can do with it is view, but with the other one ^above^ you can convert it to PDF, print, etc. Anyway, good luck