ILL is a cooperative lending service that most libraries participate in. Books are not all you will find in a bibliography. Journal and magazine articles can also be listed. Articles can be requested through ILL if your local library does not subscribe to a particular journal, but you may be asked to pay for copying costs. You can also find articles in indexes that list journal citations by subject.
Indexes usually cover a subject area and include many journals in that subject.
Indexes are produced by many publishers, so the subjects used may not correspond between indexes. Try as many subject terms as you can think of to locate articles of interest. Finding information about the Middle Ages and Renaissance can be fun and challenging. Once you find it, use it. The Society is enriched by everyone learning about life in the historic Middle Ages and applying it to the Current Middle Ages.