hi, the only book I've ever come across about making saddle trees is from australian Rams Skull Press (http://www.ramsskullpress.com/crafts.html item no. 19) . It is a guide to make australian stock saddle tree though, not sure how much help is that to you. If you want some real life guidance, I suggest you contact some saddle maker who makes his own trees (like Kent Frecker http://www.freckerssaddlery.com/saddle_tree.php or such) and see if they will teach you, or at least show you how it's done.