Blood's ability to coagulate is a cascading system with over 30 parts. Remove one part and it's fatal for the individual. How could a system like that evolve gradually over time?
He lists quite a few such systems. Bacteria having motors, the cell's operational system, the anti-body system (again a cascading system of large complexity).
These things that are claimed to fall apart when a single step is removed were not there from the ground up to provide that specific function, separately they would have provided different functions and when they fell together in a certain way provided a huge benefit. The little bones in our ears were a part of our skulls before they were requisitioned by the ear.
The issue seems to be that the argument looks at how things are and assumes that it was the only thing that these parts have ever been working towards. That any steps in between were useless until put together in this way. Where it is more accurately a bunch of different things coming together to perform all these different functions.
From what I remember from the book the coagulation system looked to be one monolithic piece and not built up of smaller systems.
Also, I did give further reading with the selfish gene for a specific example of a bacteria's flagellum.