Santisima Muerte Trilogy: Altars, Prayers, and Rituals; with added materials - The only book you need to get started working with Santisima Muerte
La Santisima Muerte: A Mexican Folk-Saint by E. Bryant Holman - as far as I know, the first book in English that covers the subject. Bryant was a dear friend, and I had the pleasure of conversing with him during the creation of this text.