For those who love iA’s Writer app, Justin Blanton has examined details of its visual and typographic design:

• Background: f5f6f6 (rgb(245,246,246)) with a touch of noise
• Font Color: #424242 (rgb(66,66,66))
• Font: Nitti Light
• Line Height / Leading: 1.5

Read more here: How to make any app look like iA’s Writer — Justin Blanton — Hypertext.net