The book Ed reads to Alex is The Sand Pebbles by author Richard McKenna.
The coordinates that Margo calculates are latitude 29.5353368, longitude -095.1114655 (29°32'07.2"N, 95°06'41.3"W). That location is a field near the OneLife Church on Old Galveston Rd. in Houston.
This episode takes place in August 2003.