You can't start talking about performance without hearing about WebPageTest. It's by far the most complex and useful synthetic tool available these days. I've been using it for quite some time and decided to brush up my knowledge by reading Using WebPageTest, by O'Reily Media.
Back to basics
The book says clearly on the cover: "...for novices and power users" so you've been warned. I've been using WebPageTest, on and off, for years. If you are in the same situation, you might find that 70% of the book is too obvious or just common sense, after all, WebPageTest is a pretty self explanatory tool.
Hidden complexity
With that in mind, the advanced parts of the books are quite good. I was not fully aware of the script capabilities of WPT. The fact that you can give instructions to it and simulate a navigation flow is very powerful. You can simulate a login scenario by doing the following:
navigate http://www.example.com/login setValue id=u username setValue ud=p password submitForm id=login-form navigate http://www.example.com/profile/usernameOther highlights include a full chapter on Continuous Integration, with plenty of examples on how to setup WPT and Jenkins or Travis, or how to setup a private instance of WPT - which I struggled to achieve a couple weeks ago!
Took me a day and a half but I finally managed to get WebPageTest working on AWS 😅
— João Pedro Ribeiro (@jpedroribeiro) August 19, 2016
Conclusion
I definitely recommend reading this book. WPT is such a complex tool that I can guarantee you will find something new about it that you didn't know before.
Having said that, bear in mind that WebPageTest, like any other open source project, is constantly being updated and you mind find some topics presented on the book are slightly outdated.