I just finished reading Robin MacPherson's How to Maintain Languages. This is a book I've been looking forward to reading for some time as I quite enjoy his YouTube videos.
How to Maintain Languages looks at MacPherson's method for maintaining (and even improving) languages you've learned. If you don't work at them, they will atrophy over time. The majority of the book focuses on how to fit one language into your daily life, but at the end of the book it goes over how to maintain more than one. I do wish this section had been a little more in depth, but it did give a good overview.
At its heart, MacPherson's method involves finding and utilizing what he calls "dead times" during your day to maintain other languages you know. Commuting to work? Listen to music or podcasts in your target language. Waiting in a grocery line? Whip out your smartphone and go over some flashcards. Winding down before bed? Read a book in your other language.
Once you have your dead times figured out, you also need to work on adding activities that use both passive and active skills. He has a few chapters that go over both of these activities, as well as another chapter on adding in dedicated study time to improve your language skills. He also shows you how to create an immersion bubble in your home without having to move to another country in order to immerse yourself in your other language(s).
In a lot of ways, How to Maintain Languages reminded me of books like Atomic Habits and The One Thing (this was especially true during the habits chapter in How to Maintain Languages, but even the whole dead time discussion reminded me of Atomic Habits). But the discussion here was less in depth, and obviously more focused on languages rather than other habits. It was a really nice reminder of those strategies I first learned about in other books though, and, thanks to my familiarity with a lot of these concepts, I was okay with the discussion being less in-depth.
One other thing I need to mention about this book: the pictures and illustrations. The book has a lot of beautiful full page pictures of MacPherson going about his daily life. And also some really fun illustrations by Alexandra Nazario of Kuma, the bear mascot of MacPherson's Kuma brand. In many ways this book seemed like a coffee table book - it's the type of book you could very easily leave out on display and flip through when you want some language learning inspiration.
Overall I quite enjoyed How to Maintain Languages. It's got me thinking of whether or not there are ways I should tweak my current language learning habits, and has given me the beginnings of a roadmap for when I move more to maintaining my languages rather than strictly learning them.