If you are a Drupal developer looking to learn Drupal 9 to write modules for your sites, this book is for you. Drupal site builders and PHP developers with basic object-oriented programming skills will also find this book helpful. Although not necessary, some Symfony experience will help with understanding concepts easily.
Daniel Sipos is a senior web developer specializing in Drupal. He's been working with Drupal sites since version 6, and started out, like many others, as a site builder. He's a self-taught programmer with many years of experience working professionally on complex Drupal 7 and 8 projects. In his spare time, he runs webomelette, a Drupal website where he writes technical articles, tips, and techniques related to Drupal development.