When it comes to the quickly growing online textbook-rental market, Chegg is the young giant to beat. But its smaller competitor, Bookrenter , is making some impressive gains. If you look at traffic to each respective website, you can see spikes at the beginning of each semester (see chart above). Last January, Bookrenter's traffic was only 12.6 percent of Chegg's, whereas by the August peak, it was 32.5 percent. From peak to peak, Bookrenter's traffic grew 167 percent to 446,000 unique monthly U.S. visitors, according to comScore. Chegg's August traffic, however, was about the same as during the January peak: 1.3 million. The chart below, supplied by Bookrenter, shows how Bookrenter's traffic has been growing as a percentage of Chegg's. In October it was 58 percent, but that number is not as meaningful as the percentage during the peak rental months earlier in the semester.