iBooks allows us to select text, underline it, make a note on the selected text, search a word in the dictionary or the Internet, or even search within the book. Some interactive books can also play audio/video or even audio navigation using the read-aloud feature, for general books. The VoiceOver utility on your iOS device can read out a book to the user.
For VoiceOver, on your iPhone, navigate to Settings | General | Accessibility and slide VoiceOver to On. Remember that VoiceOver will change the iOS device's behavior depending on the following actions: