If you use Scalatags and like it, you will probably enjoy the following book by the Author:
Hands-on Scala has uses Scalatags extensively throughout the book, using the library to build static websites in Chapter 9: Self-Contained Scala Scripts and dynamic web servers in Chapter 14: Simple Web and API Servers. Hands-on Scala is a great way to level up your skills in Scala in general and Scalatags in particular.