MTS ( Microsoft Transaction monitor ) is a Transaction Monitor and an Object Request Broker in one box. It comes free with all flavors of NT and may well be in all flavors of Windows in the next year. MTS is needed to have easily distributed applications using COM. Without it, DCOM is a continuous headache of juggling code and communications between objects. MTS is a brilliant way to manage COM objects, groups of objects, and components - the book is a deconstruction of how it achieves this.