We have covered lot of ground in this book. The aim, as I stated at the outset, was to provide sufficient material for you to be able to use Julia in your work now. Out of necessity, this has been broad rather than deep; there are so many topics to cover, each of which could merit a book on its own.
I was told when starting this book that it would be harder to decide what to leave out rather than what to put in and this has been proven to be true. So I've listed some of the other facets of Julia that I researched but eventually omitted:
OpenGL graphics
Parallel processing
Functional programming
Symbolic computation
Econometrics
Neural nets and Bayesian statistics
Natural language processing
There is significant work by the Julia community in all these fields and many more.
Julia is a rapidly changing language, it has not yet reached the v1.0 status. It is probably better to get over the 'pain' quickly rather than go through the machinations that Perl and Python have undergone of late...