This article examines what is desirable in online reference books in science and technology and outlines a framework for evaluating their interfaces. The framework considers factors unique to these subject areas like chemical structures and numerical data. Criteria in three categories, navigability, searchability, and results, were applied to five key chemistry eresources. Some e-book publishers are taking e-books farther and changing expectations for the rest. The framework offers a guide for holding publishers accountable for developing ereference books that meet users' needs. (Contains 4 tables.)