Highly recommended Meredith Hodges' Training Mules and Donkeys - A Logical Approach to Longears is absolutely essential for anyone working with mules or donkeys. Covers riding and driving. A Guide to the Care and Use of Work Horses and Mules by Maurice Telleen Imprint Training Of the Newborn Foal by Robert M Miller contains a chapter on mule foals.
Training is covered in many of the general books about donkeys and mules .
The Complete Guide to Western Horsemanship by J P Forget is a all encompassing. Other useful driving and working books For begiiners, Starting to Drive by Sally Walrond and Breaking and Training the Driving Horse by Doris L Ganton are an excellent introductions. Competition Carriage Driving on a Shoestring by Jinny Johnson is also for novices.