Not a book but I love the Cortex podcast (website, youtube) for a more vibe-centric approach to productivity and it's great to listen through the back catalogue to see what changed over the years, because neither Myke nor Grey just had a productivity system that was perfect from the start and Grey is very open with his struggles. Episode #101 has a bit of a primer on how to get started, but don't get hung on the apps discussion and more on the parts where they talk about what if someone needs to organise their life. Yearly Themes is also great, especially since the new year is almost here, and you can expect an episode on it this month.

Little warning upfront though, the target audience is very much people who have a lot of tech in their life. You might need to filter through that, and it's easy to bounce off because it's a lot of two relatively rich guys talking about how spending money is solving all their problems. If that's too much, I understand.

From that podcast I've gotten the recommendation of Getting Things Done, which is about the trappings of organising your tasks in your head (especially relevant for people with ADHD, I think) and Triggers, which is about how the environment makes certain tasks easier or harder. Both are good, but both are business books.