At Leanpub, we actively encourage readers and authors to interact: it's all part of the Lean Publishing process.
You can usually contact an author using the "Email the Author(s)" form on their book's landing page:
Also, many Leanpub authors include an email address in a section near the beginning of their book, where they ask for feedback.
We also let authors set up an online forum for each book. If a book has an activated online forum, you can see a link to the forum, if you select the book in your Leanpub library. Here's a screenshot of what this looks like:
Many Leanpub authors will also let you know their Twitter, Instagram, or GitHub account, which can find under their picture, at the top of their author profile page on Leanpub, like this:
OK, that's it!
Are you looking for great deals on Leanpub ebooks, ebook bundles, and courses? Sign up for our Weekly and Monthly newsletter sales here!
Interested in creating your first Leanpub book? Here are some quick tutorials for our most popular writing modes: http://help.leanpub.com/en/articles/3088382-quick-walkthroughs-for-getting-started-on-a-leanpub-book