I agree with both linguaholic and Xequeo.
My suggestion is to just change to an easier and more interesting book. I always wonder if there's research to prove my hypothesis, i.e. if the study material can be understood about 70 or 80%, you'll have the highest efficiency and make the fastest progress. This is about both reading and listening.
Nowadays I don't allocate large chunks of time studying languages. I mostly read one page of Facebook newsfeed from Le Figaro, Der Spiegel, ... sometimes plus readers' comments, and memorize a few words or expressions I didn't know or know well. (I use an outdated web browser to read Facebook to avoid infinite scrolling.) Reading one page takes little time. But I do this a few times a day. Studying languages many times a day, but for a short duration every time, is efficient for me and keeps me interested.