One author that is probably not an historical author is Larry McMurtry, not only will you have fun reading him you will gain a little insight into the real history of the west. Other authors that are historical slip my mind right now but will look them up and get back to you!
Lonesome Dove is a great read as is James Mischner's Texas. Both are full of historical fact but on this subject Texas is probably best.
Another fact that is being overlooked here is that the Mexican government was trying to get volunteers to move into that area with little luck. A few isolated Spanish missions were about all there was. Hearty pioneers from the eastern U.S. moved in where the Mexicans would not, doing the jobs Mexicans wouldn't do. :-)
It was never really Mexican land but, instead was Spanish land they obtained through conquest, just as we did.
Also, don't get too riled up about truth although it is good for us to know. The only people that believe the illegal claims are the usefull idiots. Those behind the movement know exactly what the facts are and how they are twisiting them. It is leftist propaganda to rile up the ignorant, including the useful idiot media, and divide our society, no different from "there was no holocaust" and "the U.S. bombed the World Trade Center themselves".