I wrote an ebook ("Practice Makes Python", http://lerner.co.il/practice-makes-python ) for people who have learned Python basics, but want to gain fluency. I'm working on videos for a higher-tier offering, and then will start to market it more seriously.
I only launched the book about 1.5 months ago, and I'm at about $1500 in revenue. I'm definitely hoping to see greater income with the higher tiers (including video) and greater marketing. I'm also speaking with some companies about them buying site licenses of the book, which would increase the revenue even more.
FWIW I just finished a beginners python course on Coursera - Programming for Everyone (PR4E, https://class.coursera.org/pythonlearn-003/). There's no natural follow on as the course uses a book for which only the first part has been translated in to a course. There were a lot of people on the course asking what to do as follow-up; might be a lead for you.
I just signed up for your samples as 'pbhj' if you want to get in touch.
Incidentally, when one adds themselves to your email list for samples it takes you to https://lerner.leadpages.net/new-practice-makes-python/thank... but there's no route back other than using the back button. IME this tends to mean people will just close the tab, providing a route back or on to a related page might help conversions or give you chance to get affiliate conversions or what-have-you.
To my mailing list, via a bunch of blog posts (on my blog), at free Webinars I've given, during a talk a gave at the hack.summit(), and on Twitter.
I tried some ads (Facebook, Google, and Reddit) for a short time, but they didn't work -- mostly, I'd guess, because the landing page is still immature, and because I didn't give away any free chapters or other elements.
The landing page is now better than it was, and people now have a choice between buying the book right away and getting a chapter's worth of exercises and solutions over a 10-day period via a drip campaign. These improvements have definitely raised the conversion levels.
I only launched the book about 1.5 months ago, and I'm at about $1500 in revenue. I'm definitely hoping to see greater income with the higher tiers (including video) and greater marketing. I'm also speaking with some companies about them buying site licenses of the book, which would increase the revenue even more.