This is strictly a reference for patterns. That seems quite obvious, given the title, but I wish to be clear that this book does not contain very many examples of fine draftsmanship or artistic technique.
At worst (many of the animal motifs) the drawings look almost childlike. At best (some of the braided patterns) they are merely attractive at first glance. Do no expect masterful engraving or pen work, as you will find none.
However, as a broad sampling of the many types of ornamentation created in human history in non-chronological order, this makes a fine catalog. If you look to the top of each of the illustration plates, you will find titles such as "Foliage" or "Arabesques" or "Angular Plait, Norse, Lombard." This is very useful for finding authentic patterns of a similar nature.
Some of the illustrations have helpful descriptions underneath such as "Hittite Cylinder..." or "700? Bologna" which at least gives you an idea of what the origin might be. But for the most part, you're faced with "Chiusi M.I.225.7" from which you must extract various abbreviations and/or Roman Numerals to look up in the text at the beginning of the book. Of course, this ridiculously terse cross-referencing is an artifact of the original book's 1930 printing origins. Somebody needs to re-set this thing on a computer and collate the notes with the illustrations.