I am in the process of reducing/decluttering things from my life, including possessions and weight!
The book that has helped me the most with the possessions is "The Joy of Less"
This book has really helped me with reducing the items that we accumulated when my parents passed away, the emotional attachment to things is so great that we tend to hold onto to items that we personally don't really want in our life's but feel compelled to hold onto because it was our parents.
The same thing goes for items that we are given as gifts that we may not particularly like but keep and maybe even display in case they turn up.
She talks you thru from starting over to everyday maintenance and everything inbetween. They system is called STREAMLINE and each letter represents a process you do to help with the items deciding if they stay or go from your home.
She then helps you work thru each room and how to organise that room to its full potential.
I have managed to declutter over 100 items from our house so far and it hasn't even made a dent in our possessions, mainly due to me flitting from room to room. But as proven by the book I need to knuckle down and do each room completely before starting on the next! Slowly and surely I will get there - The craft/office/storage room is first!
If anyone is thinking of decluttering I can definitely recommend this book