diff --git a/AiBook_PRD.md b/AiBook_PRD.md
index d4dcff0..14d2123 100644
--- a/AiBook_PRD.md
+++ b/AiBook_PRD.md
@@ -4,7 +4,7 @@ type: prd
 status: draft
 owner: Patrick (Product)
 launch-target: 2026-09-26
-last-updated: 2026-08-29
+last-updated: 2026-08-31
 ---
 
 # 📚 AIBook.fun — Product Requirements Document
@@ -142,8 +142,9 @@ the structural answer to "how do I know this AI advice isn't hallucinated?"
 | **Costs** | Model/tool costs where known — honesty about the economics |
 | **Author & sources** | Who wrote it, when, for which vertical, with citations |
 
-**Chapters** are curated collections of these recipes, one set per vertical: Real Estate ·
-Financial Advisors · Fractional C-Suite · Higher Ed · Communities · Technology. **Editions**
+**Chapters** are substantial essays, one per vertical (Real Estate · Financial Advisors ·
+Fractional C-Suite · Higher Ed · Communities · Technology), with full Workflow Recipes
+**nested in the argument**. See [§5.4](#54-the-reading-surface-locked-2026-08-31). **Editions**
 refresh annually — which is the honest justification for a *subscription* rather than a
 one-time purchase: the content genuinely goes stale as AI changes.
 
@@ -172,6 +173,49 @@ decision, not a nice-to-have**, because the entire "living book" thesis depends
 
 ---
 
+### 5.4 The reading surface (locked 2026-08-31)
+
+People read **chapters**, not a shelf of detached cards. A chapter is a substantial essay
+for one vertical: it argues a way of working, then **nests full workflows inside that
+argument** as the proof.
+
+This is a deliberate break from treating the workflow as the only page. The workflow is
+still the unit of *practice* (and of activation). The chapter is the unit of *reading*.
+
+**Chapter page**
+- Title, vertical, edition, authors
+- Opening promise (what this chapter is for) plus a **Skip to a Try-it** control — activation
+  must not require finishing the essay
+- Essay body: sections that teach the practice (stakes, constraints, how we work here)
+- Nested **Workflow blocks** at the points in the argument they earn — not bunched in an appendix
+- End matter: further workflows in this vertical, sources, last updated
+
+**Nested workflow block** (the recipe, in full — not a teaser)
+1. Chrome: recipe ID, version, time, cost
+2. Title as the job
+3. Problem
+4. Actors
+5. Setup (tools, sample files, cost)
+6. **Safeguards before the steps** so data-handling is read before anyone pastes a client list
+7. Method, with real tool output *in* the steps
+8. Evidence
+9. Try-it (~15 min, sample data, mark complete — fires Activation)
+10. Share result (community template; events, not content)
+11. Author, sources, last updated
+
+**Addressability**
+- Every workflow has a stable ID (e.g. `RE-04`) and a URL that opens the chapter scrolled to
+  that block (and a focused/print view of the same block). Campaign samples, clone-and-run
+  kits, and Workflow-of-the-Week link here — never to an essay with no way in.
+- PDF matches this stack: chapter essay + in-place recipes. Print and web must not drift.
+
+**Non-goals for the reader**
+- No chatbot on the chapter page
+- No crypto/Web3 language
+- Nested recipes are not collapsed “click to reveal” cards that hide the Method
+
+---
+
 ## 6. Requirements
 
 Priorities: 🔴 must-have for 9/26 · 🟡 should-have (launch window) · 🟢 post-launch.