I want to know what percentage of Adult Americans will read a novel
after graduating from their last academic experience.  In other words
what percent of Adults read a novel outside of a school requirement.

Hello Philippides,
I think the first link below has the information you need, or close. I
will quote some relevant content after it.

Some book statistics, by Robyn Jackson
http://www.humorwriters.org/startlingstats.html
- “1/3 of high school graduates never read another book for the rest
of their lives.”
- “42 percent of college graduates never read another book after
college.”
- “53 percent read fiction, 43 percent read nonfiction. The favorite
fiction category is mystery and suspense, at 19 percent.” I would
assume this is part of the college graduates percentage above.

Other resources of possible interest:
Romance Statistics 
http://www.rwanational.org/statistics.stm

Suite 101 Poll Results - How many romance novels do you read?
http://www.suite101.com/poll/results.cfm/17187/4542

OpinionJournal - Leisure & Arts - “Old Europe is not worth reading” by
Terry Teachout
http://www.opinionjournal.com/la/?id=110003160
- “Not many” read serious American novels...


Google search strings used:

us novel reading statistics
novel read statistics
american novels read “how many”

I hope this has been a most helpful answer. If you have any problem
with it, do please post a Request for Clarification and I shall
respond. Thank you.

One big problem here is that the source data was not available to me
because the "jenkins Group" link that is on the humorwriters site is
not up so I was never able to find out where these statistics came
from.

The answers were close to what I wanted, but I was hoping they would
come from a hihgly credible and more scientific source.