If a book isn’t working out for you, then it’s not working out for you. Don’t get held hostage to the Sunk Cost fallacy - your time is precious, drop that book and pick up something different!
And if you are just unsure about that book, jump ahead by half of the remaining pages and check out an additional 2-20 pages at that point to see if things have improved. If it still doesn’t grab you, dump it and move on.