If your search looks like an ISBN, then the search system will try to find it and take you directly to the relevant detail page. Anything else will be treated as a text search.
The text search works on whole words only, not substrings. By default, the search will look for any words in a publication's OBNB label, which contains the publication's usual title and the primary author where applicable. You can change this to search explicitly in titles only, or for specific authors.
Text searches ignore the word "the" and any word of only one or two characters (such as "a", "an" and "of"), since these are far too common in book titles to be of much use in a search. The exception is for exact match searches, which require the entire title as stored.
Text searches are not case sensitive.