At page 163-164, we have the following lines :
… UserIdentity::authenticiate() is as follows…
But what follows is not correct and neither needed as the whole class is overwritten at page 165-166!
The method has been already described correctly at page 161-162. My observation may be wrong as I have reached only page 168.
There are plenty of typographic errors too, throughout the book.
But overall the book is an excellent read, despite poor proof reading.