I have talked about the collectible aspect of Field Notes too many times to link (the Field Notes Fascination episode of the podcast is a good place to start) but I did want to mention that I just completed my first trade for some of the books not already in my collection.
I received a Flickr mail from someone who saw one of my images with the Capsule 5th Anniversary Edition book and they asked if I had any extras to trade. I rarely do, but in this case I did have a 3-pack to spare. She had some of the versions I had been looking for, and over the span of a few emails we sorted out the details and the trade was commenced.
I sent out the above referenced Capsule memo books, plus a 3-pack of the Sound Opinions books and pen and pencils that it came with. In return, I received (from L to R) a 3-pack of the XOXO Fest books, a DDC Factory Floor version, and one of the Renegade Pencils books.
It was a great transaction where we both got items for our growing collections. 10/10 would trade again!