What comes to mind when reading the tutorial is that there is a big lack of the why and a lot of how. Tutorials should really try to tell users why things a the way they are and what exceptions apply and why. Throwing code at people rarely helps if you can't give them a good fundamental explanation for why the code is that way and what design you are trying to achieve.

There is an exceptionally good book about the FreeBSD kernel which explains the whole kernel from the boot process, scheduling decisions, access control, virtual filesystem, networking and so on, and the way they do it is by explaining why on earth they ended up with the design, what problems they had to face and how the implementation tries to mitigate problems that arise from a different design. And that is exactly what I'm looking for. Once I know what the challenges are and how to design an application around these challenges, I can just go through the API and get the rest together. But I can't work the other way around, have a ton of API and then try to figure out how to use it properly.