If you are familiar with dover books, you are already aware they make collections of royalty free art work with CD or DVD roms of that art for your use.
This book is a little different than the others and I felt it need a more detailed review.
Vintage Commercial Art and Design is based on two early books from 1900's, "Sign Painting" and "Strongs Book of Designs". The designs in these books were inspired by the Art Nouveau style.
The originals were reference guides/idea books intended for artists and sign painters of the early 20th century. As such, the art in this book are samples to inspire painters to come up with there own variations. Therefor many of the illustrations in this book are not "ready to use". A lot of the pictures contain words that are embedded into the background in such a way as to make it difficult to modify. (See image above)
This book also has dozens of period font scans in it. While not unusable, it would have been much better to actually convert these fonts into typesets you could install on your computer. It is much easier to type something in true type than cut and paste each individual letter in photoshop or other paint programs.
Most of the art is in black and white but there are some color illustrations. But the colors are so washed out as to make them useless except as inspiration for your own projects.
Should you buy this book? If you are an artist looking for inspiration, especially in the art Nouveau style, definitely. The originals this book is based upon are so expensive so it is a bargain.
If on the other hand you are looking for ready to use designs, be aware that some of the designs in this book will be difficult to modify for your purposes.
Even with this drawback, I would still say it is worth having.