Hi Bardot3,
I may not be the best to answer but here 2c worth. Full blown software of that type will cost you arms & legs.
You can track easily with tracking scripts for free anything on your site. Regards publishing, you can read my book soon - but - why not use Open Office (its totally free - a MS Word lookalike). I use it for all my e writing, write your stuff - design it, convert to PDF with all links active and put it up on your site. Use a downloader to hide your download link or it will be "stolen". Regards rebranding your "book" you need a script - there are a couple free, these allow an affiliate to put their "link brand" on your book & re-sell it.
The downloader will collect info re the buyer & and manage the payment depending of the system you use - ie a shop front or standalone script. Some shop fronts are free scripts (Zen cart etc) and handle all cataloging, payments downloads etc etc. These are just integrated into your current site - try googling ecommerce scripts.

Goodluck