May I suggest you a couple? I co-wrote a chapter in middleware for the IoT in "Internet of Things: Converging Technologies for Smart Environments and Integrated Ecosytems" (http://www.riverpublishers.com/view_details.php?book_id=176) and I think it has a good balance between the depth of its content and how it can be accessed. Another one that I like is "Problem Solving for Wireless Sensor Networks" (http://www.springer.com/la/book/9781848002029). I studied during my undergraduate and part of graduate program using it and was rather useful.