diff --git a/README.md b/README.md
index 296e0b0..0101153 100644
--- a/README.md
+++ b/README.md
@@ -8,9 +8,9 @@
 
 [![PRs Welcome](https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat-square)](https://github.com/AlbertoMontalesi/JavaScript-es6-and-beyond-ebook/pulls)
 
-# [The Complete Guide to Modern JavaScript ](https://amzn.to/2H76VUz)
+# [The Complete Guide to Modern JavaScript ](https://leanpub.com/completeguidetomodernjavascript2020)
 
-## Learn everything from the basics of JavaScript to the new ES2020 features. Practice with more than 50 quizzes and dive into the basics of TypeScript.
+## Learn everything from the basics of JavaScript to the new ES2021 features. Practice with more than 50 quizzes and dive into the basics of TypeScript.
 
 [![book-cover](/assets/banner.jpg)](http://bit.ly/2VV2LbX)
 
@@ -22,6 +22,10 @@ This book is **not** for total beginners, it does **cover** the basics of progra
 
  
 
+## 4th Edition is out
+
+Included a new chapter detailing all the new features introduced by ES2021
+
 ## Free vs Paid Version
 
 The Paid version gives you access to:
@@ -45,9 +49,8 @@ You can get the course based on this book on:
 You get the ebook on Amazon, Leanpub and other stores, check the following link to find your local amazon store:
 
 - Play Store [Ebook](https://play.google.com/store/books/details/Alberto_Montalesi_The_Complete_Guide_to_Modern_Jav?id=avqrDwAAQBAJ)
-- Kobo [Ebook](https://www.kobo.com/ww/en/ebook/complete-guide-to-modern-javascript)
 - Leanpub: [Ebook](https://leanpub.com/completeguidetomodernjavascript2020)
-- Amazon Global: [Ebook](http://a-fwd.to/jHO6m9t) | [Paperback](http://a-fwd.to/3BiBhIM)
+- Amazon Global: [Paperback](http://a-fwd.to/3BiBhIM)
 
 If you enjoyed the book please leave a review to support me and help other buyers.
 
@@ -79,7 +82,7 @@ If you want to get in touch for any type of collaboration or discussion you can
 - [DevTo](https://dev.to/albertomontalesi) at https://dev.to/albertomontalesi
 - [Medium](https://medium.com/@labby92) at https://medium.com/@labby92
 - [Github](https://github.com/AlbertoMontalesi) at https://github.com/AlbertoMontalesi
-  
+
  
 
 ## Contributions & Donations
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diff --git a/ebook/10_object_literal_upgrades.md b/ebook/10_object_literal_upgrades.md
index d6846f5..fae0a5a 100644
--- a/ebook/10_object_literal_upgrades.md
+++ b/ebook/10_object_literal_upgrades.md
@@ -23,7 +23,7 @@ const person = {
   surname: surname,
   age: age,
   nationality: nationality,
-}
+};
 
 console.log(person);
 // { name: 'Alberto',
@@ -40,7 +40,7 @@ const person = {
   surname,
   age,
   nationality,
-}
+};
 console.log(person);
 // {name: "Alberto", surname: "Montalesi", age: 25, nationality: "Italian"}
 ```
@@ -56,10 +56,10 @@ Let's look at an example from ES5:
 ```javascript
 const person = {
   name: "Alberto",
-  greet: function(){
+  greet: function () {
     console.log("Hello");
   },
-}
+};
 
 person.greet();
 // Hello
@@ -70,10 +70,10 @@ If we wanted to add a function to our object, we had to use the `function` keywo
 ```javascript
 const person = {
   name: "Alberto",
-  greet(){
+  greet() {
     console.log("Hello");
   },
-}
+};
 
 person.greet();
 // Hello;
@@ -105,10 +105,10 @@ This is how we would dynamically define properties of an object in ES5:
 ```javascript
 var name = "myname";
 // create empty object
-var person = {}
+var person = {};
 // update the object
 person[name] = "Alberto";
-console.log(person.myname);
+console.log(person.name);
 // Alberto
 ```
 
@@ -117,8 +117,8 @@ In the example given above, first we created the object and then we modified it.
 ```javascript
 const name = "myname";
 const person = {
-  [name]:"Alberto",
+  [name]: "Alberto",
 };
-console.log(person.myname);
+console.log(person.name);
 // Alberto
 ```
diff --git a/ebook/23_what_new_es2021.md b/ebook/23_what_new_es2021.md
new file mode 100644
index 0000000..d7f21ba
--- /dev/null
+++ b/ebook/23_what_new_es2021.md
@@ -0,0 +1,236 @@
+# Chapter 23: What's new in ES2021
+
+Let's get started with the first of the new ES2021 features:
+
+## String.prototype.replaceAll
+
+`String.replace` is a useful method that allows us to replace a pattern in a string with something else. The problem is that if we want to use a `string` as a pattern and not a RegEx, only the **first** occurrence will get replaced.
+
+```js
+const str = "I like my dog, my dog loves me";
+const newStr = str.replace("dog", "cat");
+newStr;
+// "I like my cat, my dog loves me"
+```
+
+As the name implies, `String.replaceAll` will do exactly what we need in this scenario, replace all the matching pattern, allowing us to easily replace all mentions of a substring, without the use of RegEx:
+
+```js
+const str = "I like my dog, my dog loves me";
+const newStr = str.replaceAll("dog", "cat");
+newStr;
+// "I like my cat, my cat loves me"
+```
+
+[Read More](https://github.com/tc39/proposal-string-replaceall)
+
+ 
+
+## Promise.any
+
+During the past years we've seen new methods such as `Promise.all` and `Promise.race` with ES6, `Promise.allSettled` last year with ES2020 and ES2021 will introduce a new one: `Promise.any`.
+
+I bet you can already tell what it does from the name of the method.
+
+`Promise.any` shorts-circuits once a given promise is fulfilled but will continue until all promises are rejected.
+
+Don't get confused with `Promise.race` because with `race`, the promise short-circuits once one of the given promises resolves **or rejects**.
+
+They have similar behavior for what concerns fulfillment but very different for rejection.
+
+If all the promises inside of `Promise.any` fails, it will throw an `AggregateError` (a subclass of `Error`) containing the rejection reasons of all the promises.
+
+We can use it like this:
+
+```javascript
+// example taken from: https://github.com/tc39/proposal-promise-any
+Promise.any(promises).then(
+  (first) => {
+    // Any of the promises was fulfilled.
+  },
+  (error) => {
+    // All of the promises were rejected.
+  }
+);
+```
+
+[Read More](https://github.com/tc39/proposal-promise-any)
+
+ 
+
+## Logical Operators and Assignment Expressions
+
+With `ES2021` we will be able to combine Logical Operators (`&&`, `||` and `??`) with Assignment Expression (`=`) similarly to how it's already possible to do in Ruby.
+
+If you skipped on `ES2020` you may not be aware of `??` which is the **nullish coalescing** operator. Let's look at an example:
+
+```js
+const a = null ?? "test";
+// 'test'
+const b = 0 ?? "test";
+// 0
+```
+
+The **nullish coalescing** operator returns the _right_ hand-side when the left-hand-side is `null` or `undefined`, otherwise it returns the _left_ hand-side. In the first example the left-hand-side was `null` thus it returned the right-hand-side while on the second example it returned the left-hand-side because it was neither `null` nor `undefined`.
+
+Moving back to ES2021 stuff, in `JavaScript` we already have many [assignment opeartors](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators#Assignment_operators) like the following basic example:
+
+```js
+let a = 0;
+a += 2;
+// 2
+```
+
+But with this new proposal we will be able to do the following:
+
+```js
+a ||= b;
+// equivalent to a = a || b
+
+c &&= d;
+// equivalent to c = c && d
+
+e ??= f;
+// equivalent to e = e ?? f
+```
+
+Let's go over each one by one:
+
+- `a ||= b` will return `a` if `a` is a truthy value, or `b` if `a` is falsy
+- `c &&= d` will return `d` if both `c` and `d` are truthy, or `c` otherwise
+- `e ??= f` will return `f` if `e` is `null` or `undefined` otherwise it will return `e`
+
+[Read More](https://github.com/tc39/proposal-logical-assignment)
+
+ 
+
+## Numeric Separators
+
+The introduction of Numeric Separators will make it easier to read numeric values by using the `_` (underscore) character to provide a separation between groups of digits.
+
+Let's look at more examples:
+
+```js
+x = 100_000;
+// 100 thousand
+
+dollar = 55_90;
+// 55 dollar 90 cents
+
+fraction = 0.000_1;
+// 1 thousandth
+```
+
+[Read more](https://github.com/tc39/proposal-numeric-separator)
+
+ 
+
+## WeakRefs
+
+From [MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakRef#:~:text=A%20weak%20reference%20to%20an%20object%20is%20a%20reference%20that,reclaimed%20by%20the%20garbage%20collector.&text=When%20an%20object%20no%20longer,object%20and%20reclaim%20its%20memory.): A weak reference to an object is a reference that does not prevent the object from being reclaimed by the garbage collector.
+
+With this new proposal for ES2021, we will be able to create weak references to objects with the `WeakRef` class. Please follow the link below to read a more in-depth explanation.
+
+[Read More](https://github.com/tc39/proposal-weakrefs)
+
+ 
+
+## Intl.ListFormat
+
+The `Intl.ListFormat` object is a constructor for objects that enable language-sensitive list formatting.
+
+Looking at an example is easier than explaining it:
+
+```js
+const list = ["Apple", "Orange", "Banana"];
+
+new Intl.ListFormat("en-GB", { style: "long", type: "conjunction" }).format(
+  list
+);
+// Apple, Orange and Banana
+
+new Intl.ListFormat("en-GB", { style: "short", type: "disjunction" }).format(
+  list
+);
+// Apple, Orange or Banana
+```
+
+You are not limited to English, let's try with a few different languages:
+
+```js
+const list = ["Apple", "Orange", "Banana"];
+
+// Italian
+console.log(
+  new Intl.ListFormat("it", { style: "long", type: "conjunction" }).format(list)
+);
+// Apple, Orange e Banana
+
+// Spanish
+console.log(
+  new Intl.ListFormat("es", { style: "long", type: "conjunction" }).format(list)
+);
+// Apple, Orange y Banana
+
+// German
+console.log(
+  new Intl.ListFormat("de", { style: "long", type: "conjunction" }).format(list)
+);
+// Apple, Orange und Banana
+```
+
+Pretty neat uh? For a more detailed look at this specification check out the link below.
+
+[Read More](https://github.com/tc39/proposal-intl-list-format)
+
+ 
+
+## dateStyle and timeStyle options for Intl.DateTimeFormat
+
+We can use `dateStyle` and `timeStyle` to request a locale-specific date and time of a given length.
+
+```js
+// short
+new Intl.DateTimeFormat("en", {
+  timeStyle: "short",
+}).format(Date.now());
+// "2:45 PM"
+
+// medium
+new Intl.DateTimeFormat("en", {
+  timeStyle: "medium",
+}).format(Date.now());
+// "2:45:53 PM"
+
+// long
+new Intl.DateTimeFormat("en", {
+  timeStyle: "long",
+}).format(Date.now());
+// "2:46:05 PM GMT+7"
+```
+
+Now let's try with `dateStyle`:
+
+```js
+// short
+new Intl.DateTimeFormat("en", {
+  dateStyle: "short",
+}).format(Date.now());
+// "7/25/20"
+
+// medium
+new Intl.DateTimeFormat("en", {
+  dateStyle: "medium",
+}).format(Date.now());
+// "Jul 25, 2020"
+
+// long
+new Intl.DateTimeFormat("en", {
+  dateStyle: "long",
+}).format(Date.now());
+// "July 25, 2020"
+```
+
+You can pass whatever locale you want and you can also pass both `dateStyle` and `timeStyle` options at the same time, choosing between the three options of 'short', 'medium', and 'long' that best suit your needs.
+
+[Read More](https://github.com/tc39/proposal-intl-datetime-style)
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