The ebook has a Github repo, here:

https://github.com/mrkline/concurrency-primer

You can fork/clone/download the repo and then convert the ebook into Kindle or epub with Pandoc, like so (this is what I run):

pandoc -o concurrency-primer.epub concurrency-primer.tex

(I can share my converted file, but I don't know which file-sharing service is permitted on HN. If anyone can give me suggestions on this, I will be happy to upload it and share my epub file.)