Install the bookmarklet by dragging the link to your bookmarks toolbar:
Or, create a bookmark manually, and change the Location property to the following:
javascript:(function(){window.location="https://www.google.com/search?tbm=bks&q=isbn:"+document.getElementById("isbn");})()
To use it, go to a page which has an element with an id of “isbn” then click on the bookmark.
You can edit the bookmark if the id is called something else (change the bit in brackets and quotes from isbn to something else) or you want to search on another index (change q=isbn to q=somethingelse).