Answer: When it’s a print book.
There are still unfortunately cases of bib records being identified and
displayed as e-books in LibrarySearch even though they are for print.
This often occurs when a bibliographic record for an e-book has been
used as the basis for copy cataloguing the print copy.
Just as a reminder, be very careful if you are adapting a record for an
ebook version when cataloguing a print book. The “Adapting an ebook
record for a print book” guidelines are available on the CDD cataloguing policy intranet page (accessible to staff of the main UL and Affiliated Libraries) and also on the libraries@cambridge documentation page (accessible to all libraries@cambridge staff). This document sets out which changes cataloguers need to make to a copied ebook bibliographic record if he or she wishes to use it as a record for the print edition. (As such, the notes can also be consulted to identify ebook records.)
Any mistakes in the 008, 007 or 006 fields in particular will cause
records to be wrongly identified as e-books in the faceting on
LibrarySearch. Leaving an ebook ISBN in 020 subfield $a will cause
merging of records for print and electronic copies on LibrarySearch, so
please do pay particular attention to these areas of the record.
Please be aware that it can take some time to adapt an ebook record in
this way, so that it may be preferable to search again for a print book
record for copy cataloguing.
Many thanks to Celine Carty (University Library) for this blog post and for all her work on this issue for ebooks@cambridge.