How I Used Astro 5 + React + Inngest to Build an AI Ebook Creator (700+ Users, $0 Ad Spend)

I've been building Inkfluence AI since October 2025 - an AI-powered ebook creator that takes you from idea to finished PDF/EPUB in minutes. 700+ users so far, entirely organic. No funding, no ads, just code and content. This post is the technical deep dive. I'll focus on the architecture decisions, the SEO system that drives growth, and a relatively new channel; AI citation optimisation - that's been surprisingly effective! The Architecture The product has two distinct halves that serve very different purposes: The App (React + Vite) The ebook editor is a full React SPA. Users pick a content blueprint (23 types: novels, cookbooks, study guides, workbooks, lead magnets), generate outlines and chapters with AI, design covers on a canvas editor, and export to PDF/EPUB/DOCX. Stack: React + Vite + Tailwind CSS v4 on Vercel Firebase Auth + Firestore for data Stripe Checkout + Customer Portal for payments OpenAI GPT-4.1 (mini on free/Creator tier, full on Premium) The Marketing Site (Astro 5)