This is one of my favorite gaming accessories. I keep the hard copy on hand whenever I'm running games--it's small enough to not get in the way and organized so well I can find what I need immediately. I keep the PDF in my Dropbox so I can access it quickly when I'm doing mental prep on the go. The inclusion of a blank page--which you can fill in with some of the 1E stuff not included (I'm guessing for OGL reasons) or your own homebrew monsters--is a nice touch. If you run B/X or Labyrinth Lord and, like me, you're a more improvisational DM who sometimes struggles with too much stuff at the table, this is absolutely great.