John Keats interprets the nature of King Lear to be rather tedious. He talks about "golden-tongued Romance with serene lute" which could easily be reflected in Lear's tranquil, half-witted mindset which fails to read between the lines.
He refers to Lear's daughters (Goneril & Regan) as innocent appearing yet seductive devils. A good example of nothing imagery from the play is evident when Keats' writes "Shut up thing olden pages, and be mute". He is obviously telling us that Lear should keep his thoughts to himself and showing us that nothing is actually sometimes more productive than something useless.
Keats' believes that Lear should leave before another destructive dispute conspires ("Adieu! For once again the fierce dispute"). This is another example of nothing imagery because Lear would be better off doing nothing rather than doing something pointless and engaging in battle.
He thinks that Lear's nature is a fierce battle between condemnation and impassioned clay. What Keats' could be attempting to say is that we as readers must "burn through" the play and understand what Shakespeare is actually telling us.
He continues with "The bitter-sweet of this Shakespearean fruit." This line could relate to the tragic happenings which occur throughout the book due to the ignorant attitudes of Lear and Gloucester. Consequently the compassion returns to the play which completes the "bitter-sweet" term of Shakespeare's "fruit".
Keats' seems to be asking our ancestors to help him in his daily life to avoid the mistakes made by Lear and uses his wandering through the storm like a deranged lunatic as an example. "Let me not wander in a barren dream" is a good example of this. He is obviously referring to Lear's antics throughout the storm.
As Keats' concludes this acclaimed sonnet, he prays that ...