Totally agree that this issue is important, though Miller did not take over writing control until issue 168, which makes it double-key since this was also the 1st Elektra appearance. That is THE KEY book of the entire run because this is when Miller took the character down a darker path than seen before.
Not sure why CGC doesn't note that on the label.
158-161: Roger Mckenzie (writer), Frank Miller (penciller)
162: Michael Fleisher (writer), Steve Ditko (penciller)
163-164: Roger Mckenzie (writer), Frank Miller (penciller)
165-166: Roger Mckenzie & Frank Miller (writers), Frank Miller (penciller)
167: David Michelinie (writer), Frank Miller (penciller)
168: Frank Miller (writer), Frank Miller & Klaus Janson (pencillers)