Active reading is the combination of reading with critical thinking and learning, and involves not just reading per se, but also underlining, highlighting and commenting. We have built the XLibris™ “Active Reading Machine” to explore the premise that computation can enhance the active reading process. XLibris™ uses a high-resolution pen tablet display along with a paper-like user interface to emulate the physical experience of reading a document on paper: the reader can hold a scanned image of a page in his lap and mark on it with digital ink. XLibris™ monitors free-form ink annotations made while reading, and uses these to organize and to search for information. Readers can review, sort and filter clippings of their annotated text in a “Reader’s Notebook.” Finally, XLibris™ searches for material related to the annotated text, and displays links unobtrusively in the margin. XLibris™ demonstrates that computers can help active readers organize and find information while retaining many of the advantages of reading on paper.