From the reviews:

„Digraphs (directed graphs) are a long-standing and important field of graph theory. Nevertheless, this is the first comprehensive monograph devoted to the subject. As a handbook, it addresses various groups of readers (students as well as researchers, and from various areas of applications). Throughout, because of their importance for applications, emphasis is on algorithms (in form of constructive proofs whenever possible). … a valuable and indispensable reference for many years to come. Readers and users will be thankful!“ (P. Schmitt, Monatshefte für Mathematik, Vol. 141 (1), 2004)

"“This is a very comprehensive volume on directed graphs and related topics… [an] impressive, well-conceived, and well-written book... it is an excellent reference…[useful] for a series of seminars, where each student would be responsible for presenting a part of the material, including proofs that are in the book and proofs that are not in the book…unlike in a large number of research monographs, the authors do an excellent job putting their topic into context. Hence the book will be useful not just for researchers focusing on digraphs, but also for everyone else for whom digraphs are tools, and not goals…

Last, but not least, an extensive list of conjectures and open questions is included in every chapter. These are typically very well presented and easy to understand. I am not taking a big risk when I predict that with the help of books like this, the area will continue to progress at a fast pace.”(Miklós Bóna, MAA Online )