To begin setting up Siri to read your books aloud to you, go to Settings > General, then scroll down to Accessibility. Tap Speak Selection, slow down the speaking rate a bit to make Siri's reading somewhat more natural sounding, and then turn on Highlight Words so that you can see where Siri is reading in the iBook. There. It's that simple.
Thanks to Macworld UK's Mark Hattersley.
Thanks to Macworld UK's Mark Hattersley.