The product is a book titled "Stained Glass" edited by M.J. Gradl, featuring authentic Art Nouveau stained glass designs in full color. The book showcases the beauty and intricate patterns of Art Nouveau style through stunning stained glass art. The language of the book is English, making it accessible to a wide audience interested in learning more about this unique and elegant artistic movement. This book would be a valuable resource for anyone looking to explore the art of stained glass and the Art Nouveau style.