From Substack to Book Deal: A Playbook for Substack Writers

Is there a path from posting to published for Substack writers in 2025?

In 2025, the quickest path to published isn’t a viral TEDtalk or hit podcast. It’s having a growing Substack. Publishers are actively scouting innovators and thought leaders in their fields with engaged audiences, as well as founders who treat their newsletter like a book-in-progress.

If you’re interested in growing an audience on Substack and transforming your newsletter into a book, here’s the playbook you need to get you from posting to published.

1. Define Your World

If your Substack feels like a grab-bag of random posts, push pause on your posting schedule. Think about what kind of world you’re inviting your readers to when they land on your newsletter.

Publishers, agents, and readers want to see a cohesive throughline, so think about:

• What problem do you help your readers solve?

• What do you want readers of your newsletter to walk away with?

• What’s one part of your journey as a founder, a CEO, an influencer, an innovator that you want to share in depth about in your newsletter?

Think of your newsletter as draft zero of a manuscript.

2. Consistency > Virality

Agents and editors don’t care about one viral post. Showing up for your readers week after week with quality writing shows you’re reliable and able to scale an audience.

So be ready to show up week in and week out if you’re serious about scoring that six-figure book deal off of Substack.

3. Focus on Growing Engagement

Here’s the basic math when it comes to Substack:

10k disengaged subscribers are worth way less than 2k who consistently comment, click, and share.

The real hack to Substack growth is engagement. And when agents and publishers are looking at newsletters, they’re not looking at your subscriber count.

They want to see that your audience is actually reading and resonating with your words.

4. Create Your Anchor Series

On Substack anchor content sits at the intersection of your unique voice and the specific value you’re able to bring your readers.

A recurring feature on your Substack — like Rachel Karten’s weekly strategy sends for Link in Bio — anchor your presence on Substack. And they can be the building blocks for future book chapters.

5. Begin Developing a Book Proposal

One of my absolute favorite writers on Substack, Leigh Stein, pointed out that writing is not the same thing as content. Writing on Substack sits somewhere in the middle, making it a great place to try out and develop ideas without all the pressure of being perfect.

Once you’re a few months into writing on Substack, you can start shaping the raw material of your posts into the elements you need for a proposal.

Mine your posts for:

• A synopsis of the book you want to write.

• Audience analytics.

• Comparative titles.

• A chapter outline (just build it from your most engaging posts!)

6. Leverage Newsletter Metrics in Your Pitch

Here’s a cheat sheet for some numbers agents love to see in a Substack writer in 2025:

• Opens rates about 45%

• 1k+ paid subscribers

• Consistent growth month after month

Why do these metrics matter? Because they are proof of demand. They show that people want to read what you have to say on a consistent basis.

Mistakes to Avoid

I say use Substack as your personal laboratory and go with your instincts as a writer. But there are a few pitfalls to consider if you’re trying to grow a Substack that gets the attention of agents and publishers:

• Treating Substack like your personal diary with no clear audience focus

• Posting only when you feel inspired instead of building a consistent rhythm

• Waiting until your subscriber growth stalls before finding help

So, ready to turn your newsletter into the engine that’s going to build your book?

The Serial, a new service for creatives, founders, and anyone looking to grow on Substack is designed for exactly this. Part strategy service, part ghostwriting, subscribers to The Serial get monthly support as you plan your content, grow your audience, and shape your newsletter into a book proposal publishers can’t ignore.

Want to turn your Substack into a newsletter that scales and sells? Join The Serial.

Beta rounds are now open for The Serial. Click here to learn more.

And if you’re not ready to go all in, I am offering Substack Audits for a limited time.

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