I would start (and maybe you've already done this) by writing down bullet points of the main ideas of the chapter. Then expand and flourish each one a little, then put them together in a coherent paragraph or paragraphs. So, I guess what I'm saying is, take a more mechanical view of what you have to write instead of your normal way of writing, which I'm assuming is similar to mine. You normally just start writing and it just comes out. That works when you are interested in a topic, but not always when you are not.

If you haven't already, give it a try.

Hang in there.