In May 2019, Acquia provided an updated version of their Ultimate Guide to Drupal. The e-book is free in exchange for your contact information. Here is the announcement from their website:
Whether you're a site builder, module or theme developer, or simply an end user of a Drupal website, you'll find new features in Drupal 8 to give you the freedom to build great digital experiences. As the foremost expert in Drupal 8, Acquia has developed this ultimate guide to Drupal 8 to help you make the most of all of the improvements.
Since 2015, Drupal 8 has made significant progress with each and every subsequent release, thanks to the dedication of the Drupal Community. As a devoted member of the Drupal Community, Acquia is committed to giving back to Drupal through code and design contributions, sponsoring events around the globe, and sharing our knowledge and enthusiasm.
This information-packed eBook outlines major changes, and will get you up to speed on enhancements that empower every user.
Released on May 1, the newest version of Drupal, Version 8.7, accomplishes this task, making page layouts, media management and decoupled web experiences easier to manage and deliver, conserving production time and effort.