A couple of links about Moleskine’s Postal Notebooks:
A review at Inktronics: Special Guest Post by Bogon07 Moleskine Postal Notebook

The review is hand-written in the notebook itself, over several pages including the one below:

The bleed-through looks pretty bad with those fountain pen inks, so using other types of pens or pencils is recommended.

And a short post at the book publishing blog Galleycat (hat tip to Paul Evans for sending me the link): Moleskine Postal Notebooks Combine Writing Book & Letter

They talk about these notebooks being a nice way to rekindle an interest in letter-writing, particularly in the age of social media:

Earlier this summer, Michele Filgate wondered “Will social media kill writers’ diaries?“ I think letter-writing is a casualty of that same impulse. We spend so much time reading and writing fractured pieces of our experience that we forget to tell our story in the broad strokes of a diary or letter.

I like the idea of sending a letter in this tidy little format, though I’m not sure I’d actually do it, mainly because the person I would write to at that length would probably be with me on the trip! With other friends and family, I’m more likely to send a postcard, and even that starts to feel strange if you’re traveling in a place where you’re able to post instant updates on social media. But I have to say, I wish other people’s letters to me over the years had been written in these. Letters are so messy to store! I used to have shoeboxes full of them, as well as accordion files and inter-office envelopes. Some were unfolded sheets, others were still folded into envelopes. The envelopes themselves were often decorated, and it was nice to see a variety of stamps, and to be reminded of old addresses where my friends and I used to live. When I went through my old letters, I was awestruck at the creativity that was put into them, and the thoughtfulness and intimacy of that communication, even with some fairly casual acquaintances. But I felt like I was starting to live in a firetrap with all that paper! I had to get rid of a lot of them. But small notebook-sized items are so easy to organize and appealing to the eye and hand. If someone went through the trouble and expense to send me a letter in a Moleskine Postal Notebook, I’d probably keep it forever.