[Promotion-technology] About synthetic-speech audio books

[Oso Calmo]

Hi all,

Nowadays, electronic books are becoming more and more important, specially 
with the ones that one can read on iPhone, iPad, etc.  I have also heard 
that there are audio books too.  That is books that are read by humans and 
recorded digitally and sold.
Are there also audio books made with synthetic speech in stead of natural 
human voice?
In that case, are they commercialized?
If so, where could I buy such books?

Thanks.