The Journal of Consumer Psychology publishes research articles that contribute both theoretically and empirically to the understanding of the psychology of consumer behaviour.
http://www.journals.elsevier.com/journal-of-consumer-psychology/
The Interaction Design Foundation provides a wide range of literature on user experience design to improve experiences online. Many are useful for the consideration of user experiences in online shopping, to encourage people to purchase more online. For example the causes of shopping cart abandonment, homepage design for mobile ecommerce, and persuasion techniques to purchase more online.