Scholastic published the first official Harry Potter coloring book in November of 2015. The book was wildly popular and many more followed. The Harry Potter Poster Coloring Book is a variation on the first book. It took 20 pictures from that book and turned them into posters that you can color.
The cover of this book says that it has exclusive illustrations, but I've been unable to determine what they are. I contacted Scholastic about this and will let you know what they say. But we do know that this book differs from the original in several important ways.
First, the images are printed on high-quality card stock that can be removed, so you can frame or hang your completed pages. Second, the illustrations are printed on one side of the paper, so the backs are always blank. This is wonderful for people who don't want to have to choose which side of a page to display.
It is too soon to know if this book will have full color images of the art at the back of the book, like the other coloring books in this series, but I would be surprised if it didn't. Also, the art was designed by multiple artists, including MinaLima, which gives a nice variety to the works.