Arcadia Publishing Postcard History Series: AUSTIN by Don Martin - "...it shows an interesting side to Austin recorded through photographs and illustrations on postcards sold at roadside stands, gas stations, and in department stores."
Schiffer Publishing: San Antonio Past, Present, & Always by Mel Brown - "...juxtaposes archival postcard views with either a modern card or a personal photo to show what change, if any, has occurred to the buildings and locations that make up San Antonio . . ."
Texas A&M University Press: Taming The Land - The Lost Postcard Photographs of the Texas High Plains by John Miller Morris - "The stories the cards tell - not just the images they capture but also the messages they carried - add an exceptional dimension to our understanding of life in rural Texas a century ago."
These books are available at many local outlets or through online sellers.