According to the Latino Holiday Book (2004):

"An indigneous Mexican celebration, Día de los Muertos (Day of the Dead), November 2, should not be confused with Halloween, October 31, All Saint's Day November 1, or All Soul's Day, November 2. Instilled into the native populations by Spanish missionaries, the holiday does share a date and the same religious overtones as All Soul's Day, but its roots are firmly planted in native folklore and tradition." [...T]he Day of the Dead was started by the Mexican native tribes as a means of continuing their belief in the circle of life in which death plays a part and is not to be feared."

To learn more about the Day of the Dead, check out this interactive guide from the Smithsonian Latino Center: http://www.latino.si.edu/DayoftheDead/.

Check out this article from NPR: "Day of the Dead, Decoded: A Joyful Celebration of Life and Food"

Nonfiction
394.266 BRA Skulls to the Living, Bread to the Dead: The Day of the Dead in Mexico and Beyond (2006) by Stanley Brandes
394.266 GAR Digging the Days of the Dead: A Reading of Mexico's Días de Muertos (1998) by Juaníta Garcíagodoy
394.2697 COR El Corazón de la Muerte: Altars and Offerings for Days of the Dead (2005) by Oakland Museum of California
394.2697 HAL Day of the Dead: When Two Worlds Meet in Oaxaca (2004) by Shawn D. Haley and Curt Fukuda
398.089 CAS Chicano Folklore: A Guide to the Folktales, Traditions, Rituals, and Religious Practices of Mexican-Americans (2001) by Rafaela G. Castro

Reference
REF 394.26 MEN The Latino Holiday Book: From Cinco de Mayo to Día de los Muertos--The Celebration and Traditions of Hispanic-Americans (2004) by Valerie Menard