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, Second Edition: 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.
PDF Forms Using Acrobat and LiveCycle Designer Bible This is not a required read, but rather a great reference book for your toolbox.
JavaScript Patterns: Build Better Applications with Coding and Design Patterns This little gem helped me become a better programmer.