Reading effort
Every book is broken into four parts: writing, ideas, structure and background knowledge. Each is rated from 1 to 5, where 1 is unusually accessible, 3 is a typical adult book and 5 is unusually demanding. For writing, Diary of a Wimpy Kid is a 1, The Hobbit a 3 and Moby-Dick a 5.
The four ratings average into a score from 0 to 100, with small adjustments for pace and length. A slow 800-page book scores higher than a brisk 200-page book with the same ratings.
Up to 29 is Light, up to 54 is Moderate, up to 75 is High, and above that is Very high.
The score represents how much a book asks of a reader, not how good it is or what age it suits.
Reading profile
Pace, tone and themes: what a book is like to read, not just what happens in it. Together with reading effort, these describe the experience of the book rather than grade it.
Series order
We list a series in its reading order.
Content notes
Six areas, each marked none, mild or strong: violence, sexual content, swearing, substance use, abuse, and self-harm or suicide. Strong means the content is central, explicit or sustained. Serious subjects are named plainly in the reader notes.
Heat
For books whose main shelf is romance, heat shows how much sex is on the page and how explicit it is, on a 0–5 scale.
- 0 · Sweet: longing and kisses; no sex.
- 1 · Closed door: sex happens off the page.
- 2 · Open door: sex on the page, brief and not graphic.
- 3 · Steamy: a few explicit scenes.
- 4 · Very steamy: explicit scenes throughout.
- 5 · Erotic: sex drives the book; frequent and graphic.
We rate by the genre's own conventions. Dark romance is rated like any other romance, and its content notes say plainly what's in it. We never give a heat rating to sexual content involving characters under 18.
Where our information comes from
- Publishers' and authors' own pages, including authors' content warnings
- Library catalogs
- Wikipedia and Wikidata, for facts such as dates and series order
- Trade and newspaper reviews, and review blogs
- Common Sense Media, for books read by younger readers
We don't use other sites' star ratings, user tags or crowd lists.
How each book is checked
Every record is checked against the same written standard and reviewed independently before it's published. We also audit a random sample of published books on a regular schedule and correct anything they turn up across every book it affects.
Here, certified means checked against our written standard and independently reviewed before publication.