There’s a reason the majority of apps in the App Store look like they fit together, and that reason is Apple’s Human Interface Guidelines, a document that ensures all developers incorporate Apple-approved elements into everything they do on the iOS platform.
To make these guidelines transparent and readable, Apple has released an iPad-friendly version of its latest iOS Human Interface Guidelines reference material. Available to the public as a free download through the iBookstore, the guide covers everything from general design practices to rules about content, and features the usual iBooks flourishes such as page numbers, resizable fonts and annotation support. It also incorporates embedded videos to illustrate certain topics.
Apple’s iOS Human Interface Guidelines is available as a free 20MB download from the iBookstore, compatible with all iOS devices running iOS 4.3.3 or later, and iBooks 1.5 or later. Mac users can also access the e-book using iBooks 1.0 or later, on a machine running OS X 10.9 or above.
Whether you’re already a developer, fancy yourself as one, or simply want to get more of a sense of what makes Apple design tick, this is well worth a download.