Where should I start laying a nail down hardwood floor in this room?
I'd start in front of the fireplace with a parallel line off the same wall. Work it out so that you have a reasonably-sized finisher strip at the wall. 

You could also do the reverse and start at the bookshelves, but then you're travelling over your work for most of the job.

But this is a subjective question, so expect a variety of opinions.