I have read the book and been to a lecture by Mr. Urban. I have not attended the hands-on workshop that is currently being offered. (If I have understood the description correctly.)
I found the book very readable. Subject matter is explained concisely and well. In some of the topics, a bit brief. However, he does not claim to be an authority on all aspects of trees and soil and so for further in-depth discussion and explanations on certain aspects, he defers to an authority in that field. (For example, Philip Craul) His book comes across (to me) as a concise reference for the foundation knowledge necessary for planting and caring for trees and then the actual application of incorporating trees into the urban landscape, where he is indisputably an authority.
He offers several references at the end of each chapter, either books or websites which is very helpful.
This is a man who is passionate about trees and their survivability in the urban setting. Expressing the opinion that a landscape design has failed if the plants themselves do not survive due to a lack within the design.
He tries to offer realistic solutions to difficult problems and his experience in this field cannot be disputed. He was not shy about discussing the pros and cons of various methods, realizing that there is never one answer to the multitude of questions.
I found him very easy to listen to, as he presents his topic with a personal note of commitment.
"The Functional Tree...they must be large enough to shade houses, pavement, cars and people. Each tree should expect to live long enough with minimum maintenance so that its benefits are not outweighed by the cost of maintenance and replacement. There are many situations in which a small tree is appropriate, but small trees do not offer the environmental benefits large trees provide. This book is about increasing the quantity and quality of large trees in our communities." Up By Roots, pg ix
To me, this summed up his message during his lecture.
Sylvia