If you have read either version of my book, I sent you to a URL that uses the Azure Data Explorer to play around with the KQL queries. Rod Trent just posted a blog at Create and Maintain Your Own KQL Demo Environment with the New Start-for-free Cluster – Azure Cloud & AI Domain Blog (azurecloudai.blog) (good blog to follow) that gives you a free environment.
It is much like the environment in the book, but this gives you many more options including being able to ingest and query against your own data. Plus it is FREE!
BTW, if you have not followed Rod Trent on twitter (scroll to the bottom of the blog post to see how to follow him), he has a great series on learning KQL called “Must Learn KQL”. It is a must have if you work with KQL. Get the E-book and examples here: rod-trent/MustLearnKQL: Code included as part of the MustLearnKQL blog series (github.com)