NNELS is constantly adding ebook and audiobook content to its collection. We purchase these files from third parties, such as distributors (like Blackstone Audio, Recorded Books, eBOUND & DeMarque) and publishers. Along with those files come all the metadata records, which need some "massaging" before they can be processed in the NNELS repository.

Here is guide to updating records in Drupal:

https://bclc.wiki.libraries.coop/doku.php?id=public:nnels:cataloguing:metadata-cleanup

The basics of updating in Drupal apply to editing records in MarcEdit (ie: the title format, where to find creator information, which genres to use, etc.)