If you program for a nontechnical audience, you find yourself at a high risk that users will not read your carefully worded and enlightening error messages, but just click o
From my experience: you don't get users (especially non-technical ones) to read error messages. No matter how clear and understandable, bold, red and flashing the message is, that you display, most users will just click anything away that they're not used to, even if it's "Do you really want to delete everything?". I have seen users click the "window close"-icon instead of "OK" or "cancel" even though they didn't even know which option they chose by doing so ...
If you really need to force users to read what you're displaying, I'd suggest a JavaScript-Countdown until a button is clickable. That way the user will hopefully use the waiting time to really read what he's supposed to. Be careful though: most users will be even more annoyed by that :)
I furthermore like your idea of a "read more"-link, although I doubt that will get users more interested that just want to get rid of the message by all means ...
Just for the record: there are users that DO read error messages but are so afraid that they won't do anything with it. I once had a support call where the customer would read an error message to me, asking me, what he should do. "Well, what are your options?", I asked. "The window only has an 'OK'-button.", he replied. ... mmh, hard one :)