Architectures and techniques are described to provide customized versions of electronic books with various supplemental content items. The electronic books include a framework having core content that is provided with each electronic book and supplemental content portions that are populated with supplemental content items based on the preferences of particular readers of the electronic books. In some cases, the electronic books may include supplemental content options that are selectable to provide access to supplemental content items by readers of the electronic books. The supplemental content items accessible via the supplement content options may also depend on the preferences of the readers.