Yes, they're 4"x6", sort of a small digest size. They're shrunk down from the original to keep the price of the American edition at $9.95 each; if they were reproduced in their original size, they probably would have had to charge $19.95 per volume (or more), which adds up for 28 volumes!
That's interesting. Why the high cost? The manga I buy is full-sized, usually not reversed to America format, and costs $10, except one that costs me $8.
It does add up! Which is why I am glad the two series I'm seriously collecting are just starting to come out, I can plop down $20 every two months for the next five years and there's no huge out of pocket expense.
Most America comics, you can more or less start at any time, right? There'll be a few months of connected story, and then it goes to a different one, without a huge narratice arc? It seems like that would be necessary for a property like, say, Spider-man that's been around forever.