For anyone saying, "Huh?" right now, let me say that EIII is one of the "Apocryphal Plays" that have been credited wholly or in part to Shakespeare at one time or another but that do not have conclusive proof of authorship by Big Bill Rattlepike. In the Second Edition of the Oxford Shakespeare Complete Works, the whole text of all plays the editors are convinced Shakespeare had a hand in is printed. This means that they have made the brave decision to include Edward III, convinced as they are that Shakepeare wrote up to four scenes in the play. The text has undergone every stylistic and vocubulary test known to scholarship and there is a growing consensus that Shakespeare wrote some, at least, of this play. Now, I don't know anything about these tests, but if you'd asked me which scenes stood out as the best, I'd have picked the four that the present editors claim were by Big Bill the Bard.
The play is a straightforward history, showing Edward the III first having trouble with the Scots then invading France, where his son gets caught, massively outnumbered, in a valley surrounded by hills...Cue ridiculous triumph-against-the-odds...
Between the two are some scenes where the King meets an exceptionally attractive member of the Nobility and woos her, despite being already married himself. These scenes raise the bar in terms of the language used and feeling expressed and are reminiscent of numerous similar scenes by Shakespeare - I could easily believe he wrote them. Later, the Prince of Wales, pensive before apparently insurmountable odds of battle, finds courage whilst meditating on the inevitability of death. Once again these passages are reminiscent of other famous Shakespeare scenes.
The plot is reminiscent of Henry V and I can easily imagine that Shakespeare took this play and used it as the model for that later, greater and entirely solo effort.
What Edward III lacks are depth of characterisation, depth of feeling conveyed by the language (outside the four scenes mentioned above) and a unity in the whole. The early part with Edward's attempted adultery seems disconnected from the subsequent invasion of France.
Even taken alone, Henry V eliminates all these problems.
This play illustrates to me the genius of Shakespeare: he was able to take a populist form that demanded a continuous supply of fresh material that allowed little time for rehearsal and create work that showed such psychological and dramatic insight in such glorious language that it transcended his era to the extent of him being widely considered the best Britsh playwright ever to have lived, 400 years later.