The site searches 20,000 booksellers, popular book sites, various multinational union catalogs, special collections and national and academic libraries.
You can search by a number of criteria including author, title, imprint, publication years (before/after), price, first edition and keyword. As the interfaces and search options of the individual sites are different you may get no results at all if your search is too narrow, so it pays to start off with a relatively broad search. You can always edit your search later and add extra criteria.
I tested viaLibri and quickly found 1051 results with books authored by Leonardo Da Vinci. You can try it too.