For years I've kept an art journal of one kind or another and I've often made the books by gutting a discarded book and rebinding it with my preferred papers. But right now I prefer coil bindings over sewn bindings because I can fold the pages back on themselves for more comfortable working.
My journals aren't sketchbooks although they contain many sketches. They aren't diaries although they contain many personal observations. They could more accurately be called repositories because this is where I keep notes, lists, art ideas, workshop notes, sketches, web addresses, gallery show announcements, images from magazines, and pictures of my grand kids, among other things. They're quite colorful and once I get a few pages done in a book it compels me to keep going. Sometimes when I'm painting I'll swipe some color across a blank page so the page isn't so difficult to mess up with something else... it's my way of getting around the fear of the blank page.
I'm not alone in this love affair with the blank book. I'm currently devouring Danny Gregory's newest book about journaling, An Illustrated Life. Danny features the sketchbooks of 50 artists, illustrators and designers, giving them each 4 to 6 pages to showcase some of the pages from their own journals and giving each of them a voice to tell the reader when, where, why and how they journal. If you keep a sketchbook or journal I recommend that you buy this book and read every word. The book has "meat", heft, real content and if you aren't inspired to spend more time drawing I'll be very surprised. Danny's original book, Everyday Matters, emphasizes that anyone can draw. I believe that. It just takes practice, every day practice, because you see, drawing everyday does matter.