The Stanford Linear Accelerator Center (SLAC) and Deutsches Elektronen Synchrotron (DESY) libraries have been comprehensively cataloguing the High Energy Particle Physics (HEP) literature online since 1974. The core database, SPIRES-HEP, now indexes over 400,000 research articles, with almost 50% linked to fulltext electronic versions (this site now has over 15 000 hits per day). This database motivated the creation of the first site in the United States for the World Wide Web at SLAC. With this database and the invention of the Los Alamos E-print archives in 1991, the HEP community pioneered the trend to "paperless publishing" and the trend to paperless access; in other words, the "virtual library." We examine the impact this has had both on the way scientists research and on paper-based publishing. The standard of work archived at Los Alamos is very high. 70% of papers are eventually published in journals and another 20% are in conference proceedings. As a service to authors, the SPIRES-HEP collaboration has been ensuring that as much information as possible is included with each bibliographic entry for a paper. Such meta-data can include tables of the experimental data that researchers can easily use to perform their own analyses as well as detailed descriptions of the experiment, citation tracking, and links to full-text documents.