Yeah, I think it's correct, except for you have to include what I say in the text above it, about "if you had properties for those things, like Title and Author…" If you just look at the code, and compare it to the code in the earlier chapter, it does seem wrong. Until you add in those properties. There's probably a better way to write that whole paragraph/section to not be as confusing. I'll take the blame for that. :)
In related news, though, it looked like in my book, that the code you're talking about says Bookbook, where it should say Book book…. I left out a space there. I've got so many copies of my own book at various stages of development/writing that I'm not sure whether the final version that you have had that typo or not. (I don't know if I was looking at the most up-to-date version of my book or not, though I think I was.)