They are really great but annoying to purchase because they are such chunky comics and postage fees become a nightmare haha!
It’s one way that ancient mew was distributed in Japan. Little film sleeve inside the magazine hold the card. There are some pictures and info in this link here:
You’ll find lots of listing on buyee but just be careful because some are just the book, some are with the card but not the actual card that came with it, some are original card and book and some are sealed.
Really love the big Lugia though.