This will echo previous reviews, but it's such a good book I had to write a review myself. Sue explains the psychology of hoarding (see how many features you recognise in yourself!) and how to overcomes these; and includes humourous examples to illustrate her points.
For those of us who are faced with such a challenge that we've no idea where to begin, she gives clear guidance on how to start, suggesting different methods which will suit different personalities. For example, if you don't have much time, set yourself five minute challenges (chuck out all the pens which don't work; go through your sock drawer). Something that is easily forgotten is the need to reward yourself, and inspire yourself not to let it slide. Put a vase of flowers on your now-clear table so every time you see it, you will admire all your hard work!
After reading this book, you will be inspired to leap off the sofa and start decluttering...