Sure it is a cool photo, but what is it of? And does it have any relationship to the topic of the book?
The cover photo shows the siq, or defile, leading to the ancient Nabatean city of Petra in present-day Jordan. This is a narrow, winding passage cut deep into the sandstone primarily by natural geological forces, though it was improved by the Nabateans.
Petra was a thriving spice trading city. Its prosperity can be linked to several factors, including its location on important trade routes, its access to water through sophisticated hydraulic engineering, and its easily defensible character. The siq played an important role in the latter two aspects. Water conduits were built into the walls of the siq. Meanwhile, the floor of the siq was just wide enough for a single-file merchant caravan of camels, while remaining too narrow to serve as a route for attack.
Operating systems and middleware provide a conducive environment for application programs to interact in a controlled manner, much as Petra must have served for spice merchants 2000 years ago. Access to communication and resources remain as important as then, but so does the provision of tightly controlled interfaces that ensure security.