GENEALOGICAL RECORDS IN TEXAS
by Imogene Kinard Kennedy and J. Leon Kennedy. Baltimore, MD: Genealogical Publishing Co., Inc., 1987, 1992. At long last, I'm finally getting my own copy of this book! I found it to be very helpful in my initial research. It's got small maps of the original 36 counties, information on which records are available in places like county courthouses and the Texas State Archives, and a large chapter on the formation and organization of counties, including ones that no longer exist.