I use the unit almost exclusively for audiobooks - but many times the books I want, have never been released in audiobook format.
IF you can find an ebook copy of the book, I use "TextAloud" a text-to-mp3 conversion utility. It's fairly cheap, has LOTS of voices, and while it don't sound like a "Pro" voice actor - it's better then nothing. These days many, MANY books are available in different text formats, and there are many different text conversion programs. I get most of my ebooks in LIT format ( hate it, but that's what's out there ) convert the file to RTF, run it thru TextAloud over night, split the file into 5 minute chunks and then add the ID3 tags - now I got a custom made audiobook, sometimes many YEARS before the publisher gets around to releasing a " real" copy!