diff --git a/README-zh.md b/README-zh.md
index 9cd4090..bc42099 100644
--- a/README-zh.md
+++ b/README-zh.md
@@ -10,7 +10,7 @@ IPsec VPN 可以加密你的网络流量，以防止在通过因特网传送时
 
 我们将使用 [Libreswan](https://libreswan.org/) 作为 IPsec 服务器，以及 [xl2tpd](https://github.com/xelerance/xl2tpd) 作为 L2TP 提供者。
 
-**[» :book: Book: 搭建自己的 VPN 服务器分步指南](https://books2read.com/vpnguidezh)** [[中文](https://books2read.com/vpnguidezh) | [English](https://books2read.com/vpnguide?store=amazon) | [Español](https://books2read.com/vpnguidees?store=amazon) | [Deutsch](https://books2read.com/vpnguidede?store=amazon) | [Français](https://books2read.com/vpnguidefr?store=amazon) | [Italiano](https://books2read.com/vpnguideit?store=amazon) | [NL](https://books2read.com/vpnguidenl?store=amazon) | [PT](https://books2read.com/vpnguidept?store=amazon) | [日本語](https://books2read.com/vpnguideja?store=amazon)]
+**[» :book: Book: Build Your Own VPN Server](docs/vpn-book.md)** [[English](https://books2read.com/vpnguide?store=amazon) | [中文](https://books2read.com/vpnguidezh) | [Español](https://books2read.com/vpnguidees?store=amazon) | [Deutsch](https://books2read.com/vpnguidede?store=amazon) | [Français](https://books2read.com/vpnguidefr?store=amazon) | [Italiano](https://books2read.com/vpnguideit?store=amazon) | [NL](https://books2read.com/vpnguidenl?store=amazon) | [PT](https://books2read.com/vpnguidept?store=amazon) | [日本語](https://books2read.com/vpnguideja?store=amazon)]
 
 ## 快速开始
 
diff --git a/README.md b/README.md
index d050369..11deaf0 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ An IPsec VPN encrypts your network traffic, so that nobody between you and the V
 
 We will use [Libreswan](https://libreswan.org/) as the IPsec server, and [xl2tpd](https://github.com/xelerance/xl2tpd) as the L2TP provider.
 
-**[» :book: Book: Build Your Own VPN Server](https://books2read.com/vpnguide?store=amazon)** [[English](https://books2read.com/vpnguide?store=amazon) | [中文](https://books2read.com/vpnguidezh) | [Español](https://books2read.com/vpnguidees?store=amazon) | [Deutsch](https://books2read.com/vpnguidede?store=amazon) | [Français](https://books2read.com/vpnguidefr?store=amazon) | [Italiano](https://books2read.com/vpnguideit?store=amazon) | [NL](https://books2read.com/vpnguidenl?store=amazon) | [PT](https://books2read.com/vpnguidept?store=amazon) | [日本語](https://books2read.com/vpnguideja?store=amazon)]
+**[» :book: Book: Build Your Own VPN Server](docs/vpn-book.md)** [[English](https://books2read.com/vpnguide?store=amazon) | [中文](https://books2read.com/vpnguidezh) | [Español](https://books2read.com/vpnguidees?store=amazon) | [Deutsch](https://books2read.com/vpnguidede?store=amazon) | [Français](https://books2read.com/vpnguidefr?store=amazon) | [Italiano](https://books2read.com/vpnguideit?store=amazon) | [NL](https://books2read.com/vpnguidenl?store=amazon) | [PT](https://books2read.com/vpnguidept?store=amazon) | [日本語](https://books2read.com/vpnguideja?store=amazon)]
 
 ## Quick start
 
diff --git a/docs/images/badges/docker-stars.svg b/docs/images/badges/docker-stars.svg
index dc47ec1..c826605 100644
--- a/docs/images/badges/docker-stars.svg
+++ b/docs/images/badges/docker-stars.svg
@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="125" height="20" role="img" aria-label="docker stars: 495"><title>docker stars: 495</title><linearGradient id="s" x2="0" y2="100%"><stop offset="0" stop-color="#bbb" stop-opacity=".1"/><stop offset="1" stop-opacity=".1"/></linearGradient><clipPath id="r"><rect width="125" height="20" rx="3" fill="#fff"/></clipPath><g clip-path="url(#r)"><rect width="94" height="20" fill="#555"/><rect x="94" width="31" height="20" fill="#066da5"/><rect width="125" height="20" fill="url(#s)"/></g><g fill="#fff" text-anchor="middle" font-family="Verdana,Geneva,DejaVu Sans,sans-serif" text-rendering="geometricPrecision" font-size="110"><image x="5" y="3" width="14" height="14" xlink:href="data:image/svg+xml;base64,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"/><text aria-hidden="true" x="565" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="670">docker stars</text><text x="565" y="140" transform="scale(.1)" fill="#fff" textLength="670">docker stars</text><text aria-hidden="true" x="1085" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="210">495</text><text x="1085" y="140" transform="scale(.1)" fill="#fff" textLength="210">495</text></g></svg>
+<svg xmlns="http://www.w3.org/2000/svg" width="125" height="20" role="img" aria-label="docker stars: 501"><title>docker stars: 501</title><linearGradient id="s" x2="0" y2="100%"><stop offset="0" stop-color="#bbb" stop-opacity=".1"/><stop offset="1" stop-opacity=".1"/></linearGradient><clipPath id="r"><rect width="125" height="20" rx="3" fill="#fff"/></clipPath><g clip-path="url(#r)"><rect width="94" height="20" fill="#555"/><rect x="94" width="31" height="20" fill="#066da5"/><rect width="125" height="20" fill="url(#s)"/></g><g fill="#fff" text-anchor="middle" font-family="Verdana,Geneva,DejaVu Sans,sans-serif" text-rendering="geometricPrecision" font-size="110"><image x="5" y="3" width="14" height="14" href="data:image/svg+xml;base64,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"/><text aria-hidden="true" x="565" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="670">docker stars</text><text x="565" y="140" transform="scale(.1)" fill="#fff" textLength="670">docker stars</text><text aria-hidden="true" x="1085" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="210">501</text><text x="1085" y="140" transform="scale(.1)" fill="#fff" textLength="210">501</text></g></svg>
diff --git a/docs/images/badges/github-stars.svg b/docs/images/badges/github-stars.svg
index 987e24e..e7349d4 100644
--- a/docs/images/badges/github-stars.svg
+++ b/docs/images/badges/github-stars.svg
@@ -1 +1 @@
-<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="85" height="20"><linearGradient id="s" x2="0" y2="100%"><stop offset="0" stop-color="#bbb" stop-opacity=".1"/><stop offset="1" stop-opacity=".1"/></linearGradient><clipPath id="r"><rect width="85" height="20" rx="3" fill="#fff"/></clipPath><g clip-path="url(#r)"><rect width="54" height="20" fill="#555"/><rect x="54" width="31" height="20" fill="#007ec6"/><rect width="85" height="20" fill="url(#s)"/></g><g fill="#fff" text-anchor="middle" font-family="Verdana,Geneva,DejaVu Sans,sans-serif" text-rendering="geometricPrecision" font-size="110"><image x="5" y="3" width="14" height="14" xlink:href="data:image/svg+xml;base64,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"/><a target="_blank" xlink:href="https://github.com/hwdsl2/setup-ipsec-vpn"><rect width="54" x="19" height="20" fill="rgba(0,0,0,0)"/><text aria-hidden="true" x="365" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="270">stars</text><text x="365" y="140" transform="scale(.1)" fill="#fff" textLength="270">stars</text></a><a target="_blank" xlink:href="https://github.com/hwdsl2/setup-ipsec-vpn/stargazers"><rect width="31" x="54" height="20" fill="rgba(0,0,0,0)"/><text aria-hidden="true" x="685" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="210">25k</text><text x="685" y="140" transform="scale(.1)" fill="#fff" textLength="210">25k</text></a></g></svg>
+<svg xmlns="http://www.w3.org/2000/svg" width="85" height="20"><linearGradient id="s" x2="0" y2="100%"><stop offset="0" stop-color="#bbb" stop-opacity=".1"/><stop offset="1" stop-opacity=".1"/></linearGradient><clipPath id="r"><rect width="85" height="20" rx="3" fill="#fff"/></clipPath><g clip-path="url(#r)"><rect width="54" height="20" fill="#555"/><rect x="54" width="31" height="20" fill="#007ec6"/><rect width="85" height="20" fill="url(#s)"/></g><g fill="#fff" text-anchor="middle" font-family="Verdana,Geneva,DejaVu Sans,sans-serif" text-rendering="geometricPrecision" font-size="110"><image x="5" y="3" width="14" height="14" href="data:image/svg+xml;base64,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"/><a target="_blank" href="https://github.com/hwdsl2/setup-ipsec-vpn"><rect width="54" x="19" height="20" fill="rgba(0,0,0,0)"/><text aria-hidden="true" x="365" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="270">stars</text><text x="365" y="140" transform="scale(.1)" fill="#fff" textLength="270">stars</text></a><a target="_blank" href="https://github.com/hwdsl2/setup-ipsec-vpn/stargazers"><rect width="31" x="54" height="20" fill="rgba(0,0,0,0)"/><text aria-hidden="true" x="685" y="150" fill="#010101" fill-opacity=".3" transform="scale(.1)" textLength="210">26k</text><text x="685" y="140" transform="scale(.1)" fill="#fff" textLength="210">26k</text></a></g></svg>
diff --git a/docs/images/video-thumbnail.jpg b/docs/images/video-thumbnail.jpg
new file mode 100644
index 0000000..4207d82
Binary files /dev/null and b/docs/images/video-thumbnail.jpg differ
diff --git a/docs/vpn-book.md b/docs/vpn-book.md
new file mode 100644
index 0000000..0e1801b
--- /dev/null
+++ b/docs/vpn-book.md
@@ -0,0 +1,15 @@
+[&laquo; Back to home page](../README.md)
+
+# Build Your Own VPN Server: A Step by Step Guide
+
+This book is a step-by-step guide to building your own IPsec VPN, OpenVPN and WireGuard server. Available in eBook, audiobook and paperback formats.
+
+This book is available in: [English](https://books2read.com/vpnguide?store=amazon), [中文](https://books2read.com/vpnguidezh), [Español](https://books2read.com/vpnguidees?store=amazon), [Deutsch](https://books2read.com/vpnguidede?store=amazon), [Français](https://books2read.com/vpnguidefr?store=amazon), [Italiano](https://books2read.com/vpnguideit?store=amazon), [Nederlands](https://books2read.com/vpnguidenl?store=amazon), [Português](https://books2read.com/vpnguidept?store=amazon), [日本語](https://books2read.com/vpnguideja?store=amazon).
+
+Also available: A [comprehensive guide](https://books2read.com/vpn) to building your own VPN server, which you can find in the same book series or on the author page.
+
+Author page: https://amazon.com/author/linsong
+
+## Intro Video (YouTube)
+
+[![Intro video on YouTube](images/video-thumbnail.jpg)](https://www.youtube.com/watch?v=e5mbQCk-XPc)