This is nice. It goes straight to iBooks format and you view it there.
https://itunes.apple.com/us/book/iphone-user-guide-for-ios-9.1/id1035373510?at=10l3Vy
https://itunes.apple.com/us/book/iphone-user-guide-for-ios-9.1/id1035373510?at=10l3Vy