The article introduces a study of a small group of parents by the Joan Ganz Cooney Center. According to the article, kids age 3 to 6 remembered more narrative details from print books than from enhanced e-books with multimedia features. But  there was nodifference between the print book readers and the enhanced e-book readers when kids were asked one plot question for each story (, 2012).

If you are interested, the article has more (http://blogs.kqed.org/mindshift/2012/05/for-young-readers-print-or-digital-books/).