This book is for writers or role playing game masters that want some guide lines on developing a believable background world for their characters to adventure in. The book has some great information packed into each of it's various articles. It covers all the different facets that a person would need to consider when constructing his world. The articles have some up to date science from recent discoveries which can be very informative for science fiction writers.
Most of the articles are written by actual book writers and the articles are easy to read and understand. It is a must own book for anyone needing some help with their world background.

A lot of helpful information in here on a variety of different topics relevant to world building.