What hasn’t yet been said or written about Shakespeare’s monumental tragedy? It’s a theatrical Himalaya, a gut-wrenching dissection of two troubled families, a harrowing study of the terrors of aging, a poetic rumination on love and loyalty. When King Lear decided to divide his kingdom according to which daughter loves him best, maybe he should have come up with a better way to judge their feelings. After all, how sharper than a serpent’s tooth it is to have a thankless child.