Apple today made available the iOS Human Interface Guidelines for download with iBooks on a Mac or iOS device, and with iTunes on a computer.
Downloaded books can be read with iBooks on a Mac or iOS device. Earlier, the guidelines were only accessible for Apple developer portal. The availability of the guidelines in the iBookstore will encourage designing of iOS 7 apps simpler.
The 20 MB guide is compatible with iPads as well as Macs running iBooks on OS X Mavericks, and it takes advantage of the app with inline video playback, two-page page layouts, and built-in annotations (plus, of course, font size and color controls for reading settings) -By Federico Viticci at MacStories
The book can be downloaded for free on iOS or OS X.