Show HN: The Adventure Playbook - email signup conversion results

Earlier this week I spent an hour putting together a landing page for an ebook I'm writing about adventure (and giving it away for free). Before going to bed on Tuesday night (Sydney time) I posted the link (http://www.adventureplaybook.com) on HN. Here's the result... It's Friday morning and any traffic generated by the HN post has all but died. I've not done much else with the link and I the site now has 3576 unique visitors with 667 subscribers. That's an 18.65% conversion rate. I'm not sure if this is a good conversion rate or if it's a lot of visitors, but thought others might like to know what sort of traffic a simple post on HN got me.