Exciting Story, but to all collectors: Please be careful!

I stumbled by chance on the first volume of this series and have him swallowed up in two days. The story is beautifully written and exciting and the characters are well developed and comprehensible. The language is varied but not verkünstelt what should also facilitate English reading beginners. On the plot, I will not go into here, because the others have done before me.
What began as a book collector but something bothers me is that the volumes two and three, which of course I had ordered me immediately, thus larger of the Scripture and its format. Otherwise, the presentation is the same, so that the Order actually does not really stand that the books could differ. I picture books still ordered like to row on the shelf. In different formats just looking out a little goofy. However, I have also found at Amazon no uniform three great books of this series, because otherwise I would just again ordered me book 1 in the larger format. Apparently, these are at different issues, but this is only visible in the product description under the item format.
However, I would of course not keep those by my review of it to order these books, because then you would be a pleasure to read miss.