A couple years ago I brought a private project that shared Project Gutenberg records to your attention. Well, yesterday I thought I would go out and see if they had any more records to share so I could put them in to my Koha ILS demo site and found something awesome! Project Gutenberg has their own MARC exports (and other formats as well) that you can grab with over 40,000 records!!
If you’re using Koha, and want item records associated with these free MARC records take the file provided by Project Gutenberg and load it in to MarcEdit. Add a 942$c with your ebook type and then add a 952 with your branch and item type info. I did a tutorial video on this a while back that might help you. That’s what I did and now I have these titles in my catalog and searchable!