Are you sure that no author is listed anywhere in in the book? Remember to check both the front cover and the title page. These are the most common places to find the author’s name, but in some cases, it can also appear in other places such as the preface or other less obvious places. It is therefore worth spending some time looking through the book to make sure that any authors definitely aren’t mentioned.

Have you managed to distinguish between an edition and a print run? It’s called a new edition (ed.) if there are any content changes. If a book is exactly the same and has only been reprinted, it is called a new print run. You don’t  include print runs in the bibliography, but you must include the edition unless it is the 1st edition.