I haven't read Prison Madness, but this excellent 2009 New Yorker article by Atul Gawande is helpful in explaining why solitary confinement is one of the cruelest forms of imprisonment. My two cents: Manning's headline case should not be seen as exceptional. It should draw our attention to the fact that non-Wikileaking inmates are, as a matter of routine, held in solitary confinement -- even if, as our pal Sara from the Prison Law Blog remarks, CDCR insist on calling it something else. In addition to the maddening conditions, I frequently receive letters from inmates complaining about the strict control over reading materials at SHU units.
When reading about the imprisonment conditions of some particular inmate or other whose issue has made the news, I find it useful to think how many unnamed, invisible folk are subjected to the same, or worse, incarceration regimes. I encourage my readers to do the same.