An electronic book (“eBook”) reader application executing on an electronic device conserves non-volatile, random access memory by reading from non-volatile memory an electronic document page that includes text and at least one non-textual object (e.g., an image), storing the read electronic document page in volatile memory such that the at least one non-textual object is replaced with a placeholder that occupies less memory than the non-textual object (e.g., a blank rectangle having the same dimensions as the image), determining that the electronic document page stored in volatile memory is likely to be displayed imminently, and replacing the placeholder in the stored electronic document page with the non-textual object.