To expand on what's already been said, clicking the "Pre-Order/Purchase Book" button should take you to the promo page for the book, which will have 10-15 images depending on the number of chapters. These images were also recently made ~20% bigger (
older title vs
newer).
The upcoming subscription service will also allow you to through older magazine publications from an artist to get an idea of what sort of content you can expect, as well as potentially reading some of the chapters that will included in the book. Naturally, this would require you to have an active subscription, but if that's the case, it would be an ideal way to preview a certain artist's style.