Here's what's happening:
1.) VuFind calls WorldCat's xISBN service using the ISBN for Beginning programming for dummies (0764505953).
2.) Although this is a valid ISBN, the API doesn't like it for some reason -- it gives an "invalidId" error.
3.) VuFind isn't smart enough to detect this error. It does a search in Solr for ISBNs matching "invalidId."
4.) Solr's data normalization for ISBNs strips all illegal ISBN characters from the search string, which happens to be all of them. Thus, the search matches all other records in the index that have invalid values in their ISBN fields.
A little wacky, but hopefully that explanation makes sense. I'll fix the VuFind bug that allows this to happen in the near future… but in the meantime, you might want to take advantage of this bug to do a little bit of data cleanup, since it seems to point out a few problem records with missing ISBNs.