Continuing on the theme of our friend who considers it a lifetime milestone to read the complete works of you know who, let me ask you this: If not all, then which would you skip? Which plays are you going to recommend that your friend not even bother with? After all, we're not kidding ourselves to think that every play is another Hamlet or Lear, are we?
I'm gonna throw "King John" out. If it's not a Henry or a Richard, I don't hear anybody quoting it and I don't see anybody performing it. So other than getting the "big picture" of the histories as a whole, what else does this one bring to the reader? The casual reader is interested in getting some value out of Shakespeare's particular contribution, not a history lesson that they could have gotten from any text book.