There are many books that deal with making lye soap, each one having it's own unique input. Aromatherapy-Books.Com is a great source as are many other online and foot accessible book stores. A few books are listed below but we suggest you continually keep your eyes open as you never know where you will find a new lye soap recipe.
A few books availible from Aromatherapy-Books.Com:
"Grandma's Lye Soap" - Remwood Products Co.
"300 Handcrafted Soaps: Great Melt and Pour Projects" - Marie Browning
"The Soapmaker: Natural Handmade Soap from Your Kitchen" - Janita Morris and Juanita Morris
"Making Soaps (Handicraft Manuals)" - Paola Romanelli
"Making Soap for Fun and Profit" - Linda Inlow
"Soap: Making it, Enjoying it" - Ann Bramson
"Hand Crafted Soap" - Delores Boone