I actually picked these up at a brick-and-mortar bookstore a few weeks ago, at the same time I got a backup leather notebook for my tote bag. I love the leather with its texture, paper density, and perfectly spaced lines, but when I'm trying to break down an event sequence or character development, I HATE trying to work it  out on my pretty, non-removable pages...then I discovered these. They're just a hair smaller than my notebook, and quite thin, so I can tuck one of these straight into the middle of my main notebook, and fasten the leather cord closed around the whole kit! Now, I have an equally attractive, but less precious, space to sketch out where I'm going with a story, so more of my "main" book stays on course, and I have quickly come to adore that little pocket in the back...like others have mentioned, this paper is too thin for intense ink treatments (my uniball black and blue pens are both capable of bleeding if I try and layer a line or just pause too long) but I could care less, since my use is as a rough notes/rougher sketches space. It's pretty protected inside the other book, so I can't speak for durability, but the actual construction of the little books seems impressive to me.