The spine is just cotton fabric, and is bound with glue so the pages are able to lay completely flat when open and each page opens to a full piece of paper without having to worry about traditional signatures. I used mixed media paper, and since the pages are doubled up, I’ll be able to use lots of paint and other wet stuff when filling my book!
One thing I would say is that I wish I had used fabri-tac instead of modge-podge when gluing the pages together. As you can see, the pages warped with the moisture and the Fabri-tac would not have done. In any case, it isn’t perfect, but I love it and it is perfect for how I am gonna use it.