Absolutely wonderful! This is getting ever more close to the joy of the original home computers, and a great setup for a kid to start with especially with the book provided. The RPi4 is also an impressive bit of kit. Bravo RPi foundation!
When I was younger, I was lucky enough to have an Amiga Commodore 500+, and I read all the included literature cover to cover, over and over again. I have a lot to thank those manuals for!
EDIT: It's available for free online as a PDF, https://magpi.raspberrypi.org/books/beginners-guide-4th-ed
Anyway, if they make the board available separately, there can be a huge ecosystem of interesting cases for it.