diff --git a/README.md b/README.md
index a3984bf..6c19b28 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,163 @@ parse('foo.bar=abc&baz=def');
 */
 ```
 
+Stringifying an object:
+
+```ts
+import {stringify} from 'picoquery';
+
+stringify({
+  foo: {
+    bar: 123
+  }
+});
+
+/*
+foo.bar=123
+*/
+```
+
+## API
+
+### `stringify(object[, options])`
+
+Converts the given object into a query string, optionally with configured
+options.
+
+### `parse(str[, options])`
+
+Parses the given query string into an object, optionally with configured
+options.
+
+### Options
+
+### Default options
+
+The default options are as follows:
+
+```ts
+{
+  nested: true,
+  nestingSyntax: 'dot',
+  arrayRepeat: false,
+  arrayRepeatSyntax: 'repeat',
+  delimiter: '&'
+}
+```
+
+#### `nested`
+
+When true, nested objects are supported.
+
+For example, when parsing:
+
+```ts
+parse('foo.bar=baz', {nested: true});
+
+// {foo: {bar: 'baz'}}
+```
+
+When stringifying:
+
+```ts
+stringify({foo: {bar: 'baz'}}, {nested: true});
+
+// foo.bar=baz
+```
+
+This also results in arrays being supported:
+
+```ts
+parse('foo.0=bar', {nested: true});
+// {foo: ['bar']}
+
+stringify({foo: ['bar']}, {nested: true});
+// foo.0=bar
+```
+
+### `nestingSyntax`
+
+Sets which style of nesting syntax should be used. The choices are:
+
+- `dot` (e.g. `foo.bar=baz`)
+- `index` (e.g. `foo[bar]=baz`)
+
+### `arrayRepeat`
+
+If `true`, this will treat repeated keys as arrays.
+
+For example:
+
+```ts
+parse('foo=x&foo=y', {arrayRepeat: true});
+// {foo: ['x', 'y']}
+
+stringify({foo: ['x', 'y']}, {arrayRepeat: true});
+// foo=x&foo=y
+```
+
+### `arrayRepeatSyntax`
+
+Sets which style of array repetition syntax should be used. The choices are:
+
+- `bracket` (e.g. `foo[]=x&foo[]=y`)
+- `repeat` (e.g. `foo=x&foo=y`)
+
+### `delimiter`
+
+Sets the delimiter to be used instead of `&`.
+
+For example:
+
+```ts
+parse('foo=x;bar=y', {delimiter: ';'});
+// {foo: 'x', bar: 'y'}
+
+stringify({foo: 'x', bar: 'y'}, {delimiter: ';'});
+// foo=x;bar=y
+```
+
+### `valueDeserializer`
+
+Can be set to a function which will be used to deserialize each value during
+parsing.
+
+It will be called with the `value` and the `key` (i.e. `(value, key) => *`).
+
+For example:
+
+```ts
+parse('foo=300', {
+  valueDeserializer: (value) => {
+    const asNum = Number(value);
+    return Number.isNaN(asNum) ? value : asNum;
+  }
+});
+
+// {foo: 300}
+```
+
+### `keyDeserializer`
+
+Can be set to a function which will be used to deserialize each key during
+parsing.
+
+It will be called with the `key` from the query string
+(i.e. `(key) => PropertyKey`).
+
+For example:
+
+```ts
+parse('300=foo', {
+  keyDeserializer: (key) => {
+    const asNum = Number(key);
+    return Number.isNaN(asNum) ? key : asNum;
+  }
+});
+
+// {300: 'foo'}
+```
+
 ## License
 
 MIT
diff --git a/src/shared.ts b/src/shared.ts
index c58d4a4..48f3db6 100644
--- a/src/shared.ts
+++ b/src/shared.ts
@@ -10,19 +10,14 @@ export type NestingSyntax =
   // `foo[bar]`
   | 'index';
 
-// This is a special return value for deserializers and serializers, to tell the library
-// to fall back to using the default (de)serialize function.
-// We can't just return `null` or `undefined` etc, because we may want to deserialize to that
-export const CONTINUE = Symbol('continue');
-
 export type DeserializeValueFunction = (
   value: string,
   key: string
-) => unknown | typeof CONTINUE;
+) => unknown;
 
 export type DeserializeKeyFunction = (
   key: string
-) => PropertyKey | typeof CONTINUE;
+) => PropertyKey;
 
 export interface Options {
   // Enable parsing nested objects and arrays