How to write a Christian book: what 17 bestselling spiritual books show

Yes, when the book lets them in. The study cannot measure who reads a book, but it shows what the lasting spiritual books do on the page. They share a manner, not a softer message: plain words tied to pictures, the author's own life, and faith claims kept apart from factual ones.

The question is a live one. "Would you read a book from a Christian writer with Christian themes?" drew 300 comments on r/writers, and "Will people be turned off of my book if it has heavy religious themes?" drew 77 on r/writing. The five habits below are what the 17 books do instead of toning down their faith.

1. Plain words with a picture attached. The review asked spiritual chapters to make an idea concrete in 40% of cases, against 25% for all chapters. "Love", "peace" and "presence" are easy to read and hard to see. Lewis explains the moral law with a piano and its keys.
2. The author's own life. In 11 of 17 books, the book-level review asked for more sustained narrative from the author's experience. Across the study, chapters rich in first-person experience drew "make it concrete" notes less than half as often (17% against 38%).
3. Faith claims kept apart from factual ones. In 10 of 17 books, the sharpest argument note landed where the book stepped outside faith to claim something about science or history. The Case for Christ was told to "separate what the evidence shows from the stronger claims drawn from it."
4. Fairness to other views. Four books were asked to state opposing positions more fairly. A skeptical reader trusts a writer who puts the other side in terms its holders would accept.
5. A next step in every chapter. Sixteen of the 17 leave the reader something to practice. The Purpose Driven Life closes each chapter with a "Thinking about My Purpose" panel: a point to ponder, a verse to remember and a question to consider.

Probably not too Christian, but perhaps too abstract or too formal. The study's spiritual books read easily because of plain words, 1.48 syllables per word against 1.53 for the median bestseller. They lose readers in two other places: a long tail of long sentences, and almost no contractions. Each has a fix.

"Am I making my books too Christian?" drew 93 comments on Reddit. The data points to three things to check instead of how often you mention God.

Plain words. Keep them; they are the genre's main readability advantage. In the study, the spiritual books' lead over the median bestseller on Flesch came entirely from shorter words (4.6 points), with none from shorter sentences. Then attach each plain word to something the reader can see, because the same words drift into abstraction.

Long sentences. In spiritual books, 18% of sentences run past 30 words, against 11% in memoir and self-help. Keep long sentences for prayer, liturgy and quoted scripture, where cadence matters. Split the long sentences that explain.

Contractions. The spiritual books use 2.4 per 1,000 words, against 10.3 in self-help. Classic and translated texts pull that figure down, but even titles published since 1950 sit at 4.7. The modern bestsellers sound like a person talking: The Purpose Driven Life uses 10.0 per 1,000 words and When Things Fall Apart 10.9. A target of 4 to 10 per 1,000 means 18 to 45 contractions in a 4,500-word chapter.

Formality in your own prose is a separate problem from the scripture you quote. The Pilgrim's Progress scores 74.8 on Flesch, an easy read by formula, yet its review did not rate it highly accessible: its 17th-century diction stops a modern reader. Quote the King James Version if you love it, but write your own sentences in plain modern English.

A Christian or spiritual book should run about 60,000 to 100,000 words: the middle half of the 17 bestsellers spans 60,110 to 102,142, with a median of 80,712. That is shorter than the median bestseller in the study, at 91,574. The median book has 16 chapters, and its typical chapter runs 4,520 words.

The range inside the genre is wide, because books built for daily reading use many short chapters. Whole-manuscript counts from the study's appendix, front and back matter included:

Words per chapter is the whole count divided by the chapters, so it runs a little high. Two patterns follow. A book meant to be read a chapter a day, like The Purpose Driven Life, keeps chapters near 2,000 words, about eight minutes. A book that builds an argument or an investigation, like The Case for Christ, runs longer chapters and fewer of them. For how this compares with other genres, see how long a non-fiction book is.

Across the whole study, 23 of 46 bestsellers open chapter one on a scene or story, and one opens on a prayer. Inside their chapters, spiritual books summarize too much: the review asked 43% of their chapters to dramatize a scene instead of summarizing it, against 35% for all chapters.

Three patterns recur in the genre's notes.

• Refrains wear thin. The Power of Now was asked to "tighten the repeated 'Now/presence' formulations".
• Reflection restates the scene. Confessions was told its key scenes "are each followed by long reflective passages … that re-explain the emotion already shown".
• The logic between steps is implied. The review asked 40% of spiritual chapters to make the logic explicit, against 29% for all chapters. Mere Christianity was asked to "close the gap between the moral-law argument and the Christ claim".

The fixes follow from the notes. Open each chapter on a moment. After a scene, cut any paragraph that tells the reader what they have already felt. Between two claims, write the sentence that connects them. Close each chapter with the same named device, as The Case for Christ does with "Deliberations". If your book is closer to daily readings than chapters, how to write a devotional gives the five-part entry and measured entry lengths.

The reading level for a spiritual book should sit at Flesch Reading Ease 57 to 70, roughly grades 8 to 11. That is the middle half of the study's spiritual books; the median is 65.2, at grade 8.7. Contemplative and devotional books can sit higher, and theology and comparative religion lower. Below 57, replace long words before you shorten sentences.

Vocabulary does most of the work. Across all 46 measured books, word length explains about 70% of the variation in Flesch scores and sentence length about 14%. The spiritual books show the spread:

• The Pilgrim's Progress 74.8 and Mere Christianity 71.5: above the band, easy by formula.
• The Purpose Driven Life 69.9: at the top of the band, at grade 7.2.
• The Case for Christ 59.1: inside the band, at grade 9.4.
• A History of God 48.7 and Why I Am a Hindu 38.9: below it, closer to academic prose.

You can score a passage of your own with the readability checker on the study page.

A Manuscript AI report reads the whole manuscript and answers eight editorial questions, then gives every chapter a summary, recommendations, word count, reading time, Flesch reading ease and grade level. In a spiritual manuscript, six parts of it matter most.

• References and apparatus. Chapter recommendations flag scripture references that break a sentence, mixed formats and unexplained terms. In the study, The Purpose Driven Life tags each of its 1,918 scripture references with its translation; the Pilgrim's Progress edition reviewed mixes seven formats across 355 references.
• Testimony and argument. Where a chapter makes a claim about science, history or another tradition, the recommendations ask for evidence or a qualifier.
• Concreteness. The answer on whether your concepts are easy to follow, and each chapter's storytelling recommendation, show where an idea has no picture.
• Register. The answers on writing style and accessibility catch archaic or formal phrasing in your own prose, apart from the scripture you quote.
• Practice. The answer on the reader's next step says whether each chapter leaves one.
• Chapter length and reading ease. The per-chapter numbers let you set each chapter against the 57-to-70 band yourself.

The sample report on The Pilgrim's Progress shows what that looks like. For the chapter "The Slough of Despond" (2,178 words, Flesch 75.6, grade 8.7, an 11-minute read), the first recommendation was to move "every scripture reference to a consistent endnote or marginal system keyed to the footnote numerals, never placed mid-sentence". The report does not judge your theology, check facts or edit lines; for that, see Christian book editing.