Moving from a dissertation to a published book can be an easy process or a hard one, depending on a lot of factors. The most important difference to keep in mind is that a dissertation is in reality written for a small group of people; in my case, it was my three readers, who were technical experts in multiple fields! A book is written for a much wider audience and as such has to be handled differently. This will depend on how it is published, whether it is part of a series, the nature of the series, etc. In my case, the publisher is a European university publisher, and as such many things are done differently than with a dissertation in the U.S. I had to modify certain things to meet their standards of style. The editor also read through the manuscript with a fine-tooth comb. This was a very helpful process, as he found some typos and errors which had escaped my notice, but he also suggested many revisions which will make it a better, more useful text. Long and short answer is "it depends." If you are interested in looking into this further, a great text to guide you in the process is Beth Luey, Handbook for Academic Authors. Highly recommended to learn about all aspects of the publishing process.