This well-written text is a single source of information on one of the hottest networking topics - wireless sensor networks (WSNs).  It provides a thorough description of the most important problems and questions that have to be addressed in a WSN and gives an overview of the current state-of-the-art and puts all the individual solutions into perspective to each other.  Focusing on the protocols used in WSNs, this text stresses the close relationship between protocols and applications.