It should have been made clear to you, and the other authors, in the email - regardless of if a tweet was sent out 2 weeks ago or not.
The publisher can't assume that you read and follow everything they write. The entire agreement and disclosure should have been contained in that email to you, so you have nothing to apologize for (the fact that you didn't know that there was no free issue until you saw it here on HN says that there was a flaw in the communications process).
As mentioned in the other comments, I hope the publisher can clarify and be much clearer in his emails to potential authors next time around (perhaps publishing an 'authors' page on the website with a clear FAQ - ie. if the authors can expect their own copy, etc.)
I actually held out on insta-clicking to buy a copy when I read your comment (I still am), so clarification here will help everybody.
The publisher can't assume that you read and follow everything they write. The entire agreement and disclosure should have been contained in that email to you, so you have nothing to apologize for (the fact that you didn't know that there was no free issue until you saw it here on HN says that there was a flaw in the communications process).
As mentioned in the other comments, I hope the publisher can clarify and be much clearer in his emails to potential authors next time around (perhaps publishing an 'authors' page on the website with a clear FAQ - ie. if the authors can expect their own copy, etc.)
I actually held out on insta-clicking to buy a copy when I read your comment (I still am), so clarification here will help everybody.