Summarizing books read with DataviewJS in Obsidian

book-summary.js

```dataviewjs
const query = 'outgoing([[]]) AND #books';
const total =
  dv
    .pages(query)
    .filter(item => item
      .hasOwnProperty('pages'))
    .values
    .reduce((sum, item) => sum + item.pages, 0);

const booknum = dv.pages(query).length;
let rating =
  dv
    .pages(query)
    .filter(item => item
      .hasOwnProperty('rating'))
    .values
    .reduce((sum, item) => sum + item.rating, 0);
rating = (rating / booknum).toFixed(2);

dv.paragraph(`Number of books: ${booknum}`);
dv.paragraph(`Average rating: ${rating}`);
dv.paragraph(`Total pages read: ${total}`);
```

I include this script in a note titled "Books read in YYYY", and I link to any book that I completed reading in said year.

Each book note includes a #books tag, and at least two properties: rating (0-5) and pages. This script will then output something like:

Number of books: 4
Average rating: 3.5
Total pages read: 2432