One of the best ways to get feedback from readers is to put your email address in your book and ask readers to email you. Many of our successful authors do that!
When you create a book on Leanpub, by default we add an "Email the Author(s)" button that lets current and potential readers of your book email you with feedback and questions. Many Leanpub authors have had great success not only building up support for the book through this feature, but also receiving feedback on everything from typos to suggested new chapters, for books being published in-progress.
But one of the most sophisticated ways we provide for interacting with readers is our Forums. You can enable the Forum for your book by going here in the Leanpub menu:
Author > Books > [Your Book Title] > Community > Forum
Third-party options include creating a Slack channel, though the more connected to Leanpub your feedback channel is, the better!
Here's a more in-depth article about contacting readers:
Here is an article from our Authors Forum on this topic:
Please feel free to post there with any ideas or questions you may have!