If I were going to do it:
1) Is my book about sadomasochism? If "no", I would reconsider "Submit" as button copy. People like "Get My Free X" a lot more, which leads into...
2) "Join the conversation" sounds like something that only a marketing person would love. If you want to offer something to convince people to join your list -- and you do! -- promise them immediate value from it. There has to be an early chapter you can give away for free. If your publishers are too 19th century to cotton to that, a) they should be fired but b) you can produce something short & actionable which is spiritually aligned with the book and then give that away.
3) Microcopy to the general effect of "We won't spam you" pretty much invariably works. It's also a good idea to set expectations as to what kind of email they'll be getting and how frequently.
Agree completely about getting the button wording right. We'll try some different buttons; the 37Signals example (where they changed from "buy" to "see plans and pricing" and doubled conversions) shows this is something to spend a lot of time on. Candidly, we had only a few days to get things live, so they're still rough around the edges.
Our publishers are O'Reilly, so they're delightfully open (encouraging, even) about sharing all kinds of content. And there's simply too much for the book to hold. Great point that we should make some content just for list subscribers.
We're in the middle of interviews with a bunch of big tech companies about the metrics they watched in the early days, and we should probably put some of that aside just for subscribers.
Thanks for the feedback.
