Like many "sketchbook" programs for iOS before it, Paper provides a series of notebooks which you can customize and sketch in to your liking. The app does the notebook interface better than any of the others I've tried; it allows you to customize the cover with an image or photo from your library, skim through completed notebooks, and enter drawings, add pages, or share them with just a tap.

I love skimming through virtual sketchbooks like this: It's all the fun of browsing through someone's Moleskine, but with swiping instead of page-turning. And the graphics are top-notch; on a third-generation iPad, slowly turning a page is almost as fun as doing the drawing itself.

The free version of Paper offers a nib pen for sketching, an eraser, and a smattering of colors with which to illustrate your drawing. The pen is fairly robust for a simple sketching tool, and if you're just planning to do some writing and line drawings, it could suit you just fine.

You can add up to four additional tools (a pencil, marker, ballpoint pen, and watercolor paintbrush) for $2 each, or buy the full set for $8. I purchased the entire toolset to experiment with, but the two you absolutely have to add to your arsenal are the pencil and the watercolor brush.