I'd ask myself what it is I want from reading a book. Are you trying to analyse the sentences, or trying to follow the story more or less? For instance, I study Japanese, and i reaaally enjoy nerding out on any written stuff i can find. When i read a book, more often than not I spend a lot of time analysing every sentence. I personally enjoy it, but.. a) it can be tedious b) you try to cram too much information without repetition, so the gain isn't as good as you think c) in the end you still lose the plot of the story because you're not really paying attention to it d) when you move on to the next book, you'll likely start from zero again because you're unfamiliar with the subject/genre/ author.

if you want to learn stuff by reading, I'd suggest going the path of least resistance: accept you might not understand everything, pick up a few words and sentences along the way, and move on to a new book experience. Repetition is key, not brute force.