I was a little dissapointed when I didnt find Dan Browns The Lost Symbol in the iBook Store, I have it in pdf format on my laptop and in my quest to get it over to my iPad I found Calibre!
Calibre ebook converter is a free program for both Windows and Mac OS X and can be be downloaded for free from Calibre ebook.com. It converted The Lost Symbol in a lttle over 3 minutes. When the conversion was done I simply clicked Add to Library in iTunes 9.1 and there it was in my Books. The only catch seems to be that the cover gets a smaller format on your bookshelf on the iPad, but hey, I can live with that!