1) Fat Daisy: Inner Beauty Secrets from a Real Dog (2006) by Beverly West and Jason Bergund, photography by Jessica Alonso. A spoofy work-out book for overweight dogs, chiefly photographs of a sixteen-pound obese chihuahua seeking fat acceptance. Very weird, since a dog's diet is completely controlled by an owner, and the "fat pride" expressed in this book amounts to animal abuse, so is much more grotesque than it is funny. Daisy's cute even so.
3) Chihuahuas (2001) by Bob Temple, introduction to the breed for very small children.
4) The Chihuahua (1999) by Charlotte Wilcox, typical introduction to the breed, in the "Learning About Dogs" series covering sundry breeds one by one.