Softcover is based on the Rails Tutorial model, which differs from Leanpub in several key ways. I actually think Leanpub is a great service if it meets all of your needs as an author, and in fact if it had met all of my needs I might not have bothered building Softcover. (Of course, Leanpub didn't exist when I first started publishing the Rails Tutorial in 2009, but I might have used it for follow-on products.) Here are some of the important differences:

- Softcover comes with an industrial-strength, open-source production system. This means you can write heavily formatted books with cross-references, code listings, tables, etc., and interactively build them locally, all without being locked in to a proprietary system.

- Softcover's HTML books are first-class citizens. The online version of the Rails Tutorial is a key part of its marketing strategy, so it has to be polished and prominent.

- Softcover gives you your customer list. Letting customers opt-in to share their email is fine for more casual authors, but it isn't ideal if (like me) you're trying to build a business.

- Softcover supports custom domains. It's important to me to use a custom domain for branding/SEO and so that I own my own traffic.