The process by which you learn the details of what an author has written over his or her lifetime is known as bibliographic research. You do this by visiting the websites of certain libraries.
When authors publ;ish books they (or their publishers, acting for them) need to register copyright with the appropriate agency of the nation in which the book was first published.
In the US, copyright is registered in the U.S. Copyright Office of the library of Congress, and copies of all copyrighted books are found in the Library of Congress. An author search, with the name Gary Paulsen, sorted in ascending chronological author will pull up all his books published originally in the US.
Th old university libraries (Oxford, Cambridge, Edinburgh, Wales) and British Library serve as copyright libraries in the UK. An advanced search of the union catalogue, COPAC, in ascending date order nfor author Gary Paulsen will obtain bibliographical citations of his works held in UK libraries, including dates.
Amiucus is the national library union catalogue for Canada.