Some thoughts

To be honest, I only discovered Crystal recently. On the detour via Ruby, which I came to via Erlang/Elixir. The ways of the Lord are sometimes strange. I didn’t understand why this great language is so unknown. And it would be terrible if it simply disappeared into oblivion again. Perhaps the situation would be a little better if there was a new, more comprehensive and challenging book? For now, sponsoring is certainly the best way to keep the crew going.

Regards, Karl

If you come from Ruby, the official crystal book is really a good start.

AFAIK, there are only two books available for now.

programming crystal create high performance safe concurrent apps (older)

crystal programming (A project-based introduction to building efficient, safe, and readable web and CLI applications)