Cataloging ebooks is difficult to do well, as they are often purchased in large collections, sometimes with only low-quality cataloging copy available. MARC records may be provided upfront in a large batch, or trickle in one at a time as they become available. Records may contain links that point nowhere, to the wrong book, or to an offer to sell you the book you already own. Loading records sight unseen may introduce inconsistency or overlay good print records with poor electronic ones, making the catalog much more difficult to search.
This article describes in more detail the major challenges in ebook cataloging, record normalization and access checking, and introduces Normac: an open source web-based tool for processing MARC records.
Lybarger, Kathryn, "Keeping up with Ebooks: Automated Normalization and Access Checking with Normac" (2013). Library Faculty and Staff Publications. 74.