Great question. There is so much more we could have included, so yes definitely!
We didn't really get a chance to cover Date much. Again, while the book teaches everything you need to know to be able to look up Date and "get it", there are many nuances to how to work with dates and times that are tricky to figure out. But we ended up leaving most of that out because, while it's important, it's not really a programming fundamental in the same sense that objects and functions are (at a more general level).
Exception handling is covered (briefly) in the appendix, but that's another topic that could have been expanded a lot.