I like to use WorldCat to search for books--remember that the book you need may be in unexpected places. Also remember that the Family History Library doesn't have everything and that no library can have every published reference.
A search on WorldCat for the Roots of the Family Fecht, indicated that only four libraries had it. I was not surprised the Library of Congress had it and the one Florida library was near where the compiler lived. The family had no New England connections, so I was surprised that the New England Historic Genealogical Society had it. The Alabama State University was also a surprise for a similar reason. WorldCat doesn't know that I have a copy in my office.
One never knows where a book will be--use WorldCat to search as many library card catalogs as you can.