Stuff, which was recommended at a presentation I recently went to on hoarding, led by one of the staff members of the Institute on Aging (an excellent resource itself). Stuff was well worth a read, as it paints a portrait of the issue of hoarding that creates at least some understanding but more importantly a deep compassion for those who hoard.
I was surprised by many of the things the authors discovered in their research on hoarders and hoarding, the primary one being that hoarders are, almost without fail, perfectionists. They hoard not because they are slobs, but because they can't bear to think about what would happen if they got it wrong and threw the wrong thing away. It illustrates the psychic (and sometimes almost physical) pain hoarders feel when trying to get in control of their hoarding, and the comfort they feel in what most people see as truly unlivable conditions.
Stuff primarily presents its information through illustrative narratives of the lives of individuals, looking at hoarding through a variety of lenses. At the very end it offers further resources for people looking for help. The authors, Randy Frost and Gail Steketee, have a workbook for treating hoarding behavior that sounds very useful for those seeking personal help to change.
I do wonder if the extreme conditions used throughout the book might do a slight disservice, however, as some who may suffer more mildly from hoarding tendencies may read this and think, "Well, at least I'm not as bad as that." As the authors point out, the problem with hoarding is not the stuff per se, but the pain and distress it causes the hoarder.
As I said earlier, however, the overall sense I got from this book was one of compassion for hoarders and their families. It shows that hoarding is not a moral failing, a weakness, a sin, or consumerism run amok, but a painful and difficult problem that requires treatment and care.