Searches conducted on Halloween in 2011 revealed that Amazon's Kindle eBookstore had 2,269 eBooks with "zombie" in the title; this number increased to 4,874 by 2012 and reached 8,052 by 2013. In contrast, the Library of Congress only recorded 674 zombie books. The popularity of zombie eBooks indicates that a growing number of self-published authors are writing large quantities of novels centered around zombies. These zombie novelists include both professional and amateur writers, making it difficult to easily distinguish between them. For instance, well-known author Joyce Carol Oates, who was twice nominated for the Pulitzer Prize, published a book in 1996 titled Zombie (P.S.), where "Zombie" is the name of a serial killer in the novel.