Object-Oriented JavaScript, 2nd Edition This book, while not covering LiveCycle specifically, does give a very good overview of JavaScript programming. I am constantly reaching for this as a reference manual when programming LiveCycle Forms.
Adobe LiveCycle Designer Creating Dynamic PDF and HTML5 Forms for Desktop and Mobile Applications I recently purchased this book, and have used it extensively to supplement my knowledge base. Highly recommended!
JavaScript: The Definitive Guide: Activate Your Web Pages (Definitive Guides) Necessary component if you are designing LiveCycle forms, but only have LiveCycle Designer and Adobe Reader.
JavaScript Patterns This is not a required read, but rather a great reference book for your toolbox.
PDF Forms Using Acrobat and LiveCycle Designer Bible This little gem helped me become a better programmer.