What versions of Xcode and Swift are used in the book and video course?

The book and video course use Xcode 9 and Swift 4.

Can I get the book without the video course or vice versa?

Sure! Both the book and the video course work independently of the other. Obviously a video course is a more visual medium, but a book can be a better reference, so whichever you prefer! The book does go into some topics in more detail.

Are there challenges?

Yes! Both the book and the video course have challenges that you may want to try out yourself. Reading about it or watching someone else do it is one thing, but to retain something you've learned, nothing beats doing it yourself!