Phoenix & Unicorn project are awesome and are the most important/useful DevOps books IMO. They’re novel books & tell stories of digital transformation - changing an organisation ways of working to be more DevOps.
The reason i think these books are great because a lot of people misunderstand what DevOps truly means (thinking it as just about toolings such as IAC, Containers, CI/CD tool etc) and these books puts focus back on DevOps being more of a process/culture-shift. flow of working.