I couldn't put my phone down for a long time until I realized it was just a habit, not something magical. I started by reading "Habit" by Lola Jones (though it's not specifically about gadgets, it's really helpful for understanding how your brain rewires itself). Then I came across "The Attention Trap" by Evgeny Morozov - he takes a more critical look at how apps actually hook us, and that's more useful than just blaming your phone as the enemy.
About the previous answers - yeah, the books mentioned there are definitely worth it, but I feel like they give you too much theory. If you're looking for something with concrete steps, check out "Minimalism" by Joshua Fields Millburn and Ryan Nicodelis. They literally spell out how to get rid of digital clutter and rethink your relationship with tech. The book isn't super thick, but it's very practical.
And here's the thing: don't look for one magic book that'll solve everything. I tried different approaches, and each of these books gave me something different. It's better to read two or three different ones so you can figure out what method actually works for you - whether it's going cold turkey or gradually cutting back, turning off all notifications or physically keeping your phone away.