Operation World is a handbook of information on most countries, including their spiritual status. It gives economic and geographical information to help us understand the situations of various peoples, but the emphasis is on religious views and spiritual needs. It tells what percentages of each country's population belong to which religions. Combined with other background information, this helps us better understand various cultures.
The book is available in print, PDF, Kindle, and epub formats.
Window on the World is a version written for children by Daphne Spraggett with Jill Johnstone.