Use multiple fields to narrow your search.
If possible, don't search for strings with punctuation (apostrophes, dashes, quotes).
Spaces in search strings will be treated as 'AND'. For example, "artic exploration" will look for books with subjects that contain both terms, not subjects with either.
This search is not case-sensitive, so "Jamaica", "JAMAICA", and "jamaica" all return the same results.
Short or unusual strings get closer results, e.g. try "tolstoy" in subject, instead of "war and peace".
(Very common words, such as "and", will not generate any results.)