While I have never had the site use up that much of my processor.
The main problem most likely is one of three things, what ever they use to track where you go on the site, what novels you are reading where you read to and so on. Which we know they do.
Or the ads, Banner ads are notorious for destroying website performance. Considering one is at the bottom of every single chapter. If you load more then one chapter by scrolling on further down, you will quickly ramp up the amount of banner ads that are loading and running. I personally have seen the site uses less of my CPU when running some type of ad blocker(relax admins I turn it off for legit sites like yours). Even tho that should use up almost more because its another process running in the background.
Or you simply need to run some anti malware/spyware. Most the time it is this tho, make sure your protection is up to date and scan often. Also try clearing your cache. Because it could be all the cookies you get from ads.