Good book.
I started using TypeScript probably about a year ago when my team got assigned a project that used it. I picked up bits and pieces as I went along, and I got pretty good at using and expressing types concisely. But there were a couple of things that remained somewhat mysterious to me... declaration files, various configuration options, inference, conditional types, etc.. The very complex types people suggest on StackOverflow to solve some esoteric typing scenario read like sorcery to me. I figured I probably ought to get myself some kind of grounding in the language.
This book has been very good for my purposes. It did cover a lot of ground I had already more or less picked up on my own, but it also gave me a basic understanding of some of the more esoteric applications of TypeScript, and when they are useful, as well as illuminating the purpose and usage of the configuration options (the configuration section will remain a reference in my toolkit for some time, I imagine). I will likely re-read it in future (particularly Chapter 15, which covers Conditional Types) to shore up my understanding, because there's a lot to digest there, but for now I feel much more capable of engaging meaningfully with TypeScript-based projects.