How can Chatbots be useful in CS education?

I'm using chatbots to discuss a variety of topics with 14 to 16-year-old high school students.

By "using" I mean that they are the subject of instruction, not a study aid / instrument for the students to use to get automated answers to frequent questions and things like that. So that's probably not what the book you mentioned talks about, but I'll go on anyway because your title asks the more open

How can chatbots be useful in CS education

Chatbots are a great topic in computer science education because

• Everybody knows about them - teenagers know what chatting is and have first-hand experience of doing it, and most students have either encountered a chatbot already or they've heard about Siri and compatriots, which can be framed as chatbots for the purposes at hand.
• There are chatbots who try to mimick humans, so you can use them to discuss the Turing Test with your students
• Simple chat bots which simply look for some combination of words in the input phrase are easy to build using scripting languages such as Python, and therefore can be used to give the students a first feeling for what needs to be done in order for a computer to correctly identify the meaning of a sentence in a human language. This can easily be extended into a discussion about whether computers can "understand" us.
• Coding simple chat bots is easy enough so that it can serve as a first small project for beginners learning to program
• In my classroom experience, teenagers love spending some time writing simple chat bots and getting them to provide (often somewhat rude) answers to things their peers type in, so it's a fun topic, too.

I agree with Buffy that using chatbots as a study aid is much, much harder to get right, and I wouldn't try that unless the domain was very, very well specified.