There are so many free online sources about worldbuilding, etc. that paying good money for books about those subjects is slightly puzzing. Many, many RPG, scifi and fantasy sites and blogs contain all sorts of how-to and comments from experts and talented amateurs.
STARGAZING: All I see are the lights of a billion places I'll never go. --Howard Tayler, Schlock Mercenary
"It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change." Charles Darwin
"It is the duty of the writers to seduce me into suspending my disbelief!" Paul Beardsley