Here are a few books that have helped me.  
​Below each one is a shortcut to the corresponding author's website

Clutter Free with Kids
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Josh Becker had an epiphany one Saturday while cleaning his garage.  This book showed me why I needed to declutter not just for me but for my kids.
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becomingminimalist

The Life Changing Magic of Tidying Up

Marie Kondo is a Japanese organizing consultant who you likely have heard of by now.  She has a specific order for decluttering and even explains her own way of folding clothes.
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KonMari

​The Art of Work
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Not necessarily aimed at decluttering, but more at writing and finding your calling in life.  Jeff Goins podcast "The Portfolio Life" is one of my favorites.  He constantly interviews some of the most amazing authors.
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GoinsWriter

Ultralight
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Or any other book by Leo Babauta.  He has several for sale and also has some free eBooks for download.  If you're looking for inspiration to accomplish your goals, read his story.

Zen Habits

NOTE: The Amazon links above are affiliate links, meaning I could make a small commission for anything you purchase.