- The percentage of buyers of book N who buy book N+1.
- The most important number in series publishing.
- Healthy rates: 60-80% book 1→2, 70-90% book 2→3, 80-95% book 3+.
- Below 50% sell-through means the series isn’t holding readers.
- Calculated by comparing copy counts between consecutive books in a series.
A sell-through rate is the percentage of buyers of book N who go on to buy book N+1 — the most important number in series publishing. A healthy sell-through rate is 60-80% from book one to book two; 70-90% for book two to book three; 80-95% from there. Below 50% means the series isn’t holding readers.
Chapter i·Why it matters
Sell-through is the math of series economics. A 60% sell-through across three books means book three earns 36% of book one’s launch sales (60% × 60%). Authors who track sell-through know whether to write the next book in the series or to start something new.
Chapter ii·What to include
- A per-book copy count from each retailer dashboard.
- A simple calculation: book N+1 copies ÷ book N copies = sell-through %.
- A quarterly review: are the rates healthy?
- A diagnostic when below target: ending of book 1, back matter, pricing.
- A back-matter improvement plan if sell-through is weak.
- A "stop or continue" decision point for low-sell-through series.
Chapter iii·Example
A working fantasy author’s three-book series: book 1 sells 4,200 copies in year one. Book 2 sells 3,100 (74% sell-through). Book 3 sells 2,650 (85% sell-through). Healthy. She commits to book 4. If book 2 had sold only 1,400 (33%), she’d have considered ending the series.
Chapter iv·Related questions
WriteLoom holds copy counts and sell-through math per book in your series, so the series-level decision data is in one place.
See the Sell studio