Transmission (Store and Forward) Delay
I haven't read that book, so I may be off the mark.

Usually the transmission delay on a direct link is negligible compared with the processing delay at the endpoints and at each hop. In concrete scenarios, going via a geosynchronous satellite is the only way you have significant transmission delays on a link (about 0.2s to go up and down).

So when you have a network link that consists of a chain of direct links with a router at each hop, the total transmission delay is the sum of the store-and-forward delays on the routers. Strictly speaking, it's that plus the total length of the link divided by the speed of light (if the signal propagates at light speed), but that second part is usually negligible.