Collects Superman (Vol 1) #233-238, 240-242.
Note: #239 was a reprint.
*Originally published in 1971, this story turned Superman's status quo on its head by featuring a story in which all Kryptonite was destroyed! But that leaves The Man of Steel anything but invulnerable as his powers slowly begin to fade and a doppleganger Superman arrives on the scene with strange powers of its own. *Source: dccomics.com