Like fellow New Calvinist John Piper, Keller so deeply misconstrues the Divine Law, (Is John Piper an Antinomian? see E S Williams on 'Is John Piper Antinomian?' Amazon's link unreliable) that he repeatedly describes the elder son in the parable as keeping all its precepts well, despite harbouring self righteousness and a proud superiority that feeds both judgement of others and a bitter, critical spirit.
It's quite true the elder son is the focus of the parable and the pharisees, scribes, and their modern counterparts of all shades the Lord’s target for gentle reproof.
However read Ps. 19 or better Ps. 119 to see the ugly and antichristian* spirit of this book exposed. The author has wickedly conflated loving Divine Law with self righteousness. This is a common charge levelled by the ungodly at the saints, Job’s three Satanic ‘counsellors’ did the same. Only Elihu knew how to justify Job by exposing his utter vileness, vindicate God's Law and remind of His gift of a sinner’s ransom, Keller on the other hand has chosen to undermine and disqualify the Law severely. Elihu was angry with Job & the three counsellors for their inept & harmful remediation, so was God, he'd be angry with this companion too. When Paul explains free justification without works, he adds, 'Do we then make void the law through faith? God forbid: yea, we establish the law' (Rom. 3.31).
Never does the Lord endorse the pharisees as wholly, properly or fully keeping the Law. The author however continually chooses to differ describing them as ‘extremely good’, ‘living very moral lives’, as ‘virtually faultless regarding the moral rules’, ‘ethical’ or exhibiting ‘careful obedience to God’s law’. On the contrary the Saviour exposes them repeatedly for misuse or mishandling of the Law’s probing, convicting & spiritual character, and for hypocritical pretence that harbours a deep hostility to the commands of God's kindness. Isaiah writes of such religious hypocrites, ‘From the sole of the foot even unto the head there is no soundness in it; but wounds, and bruises, and putrifying sores: they have not been closed, neither bound up, neither mollified with ointment.’
Keller however has constructed a wholly false dichotomy between lovers of Law and lovers of sin, in the guise of the two sons. He thus violates the Lord's Law, not honouring it, as is the common task of those at enmity with it. By eschewing the instrument of diagnosis, he has also rejected the kernel of its root remedy, and the means of validating cure. He is opening the gate to freer sexual licence, the public practice of homosexuality, easy divorce and a multitude of worldly snares within the church, in express opposition to apostolic teaching. He has, as Jude warned, subtly turned grace into licence (v. 4). He is sowing tares which will be quickly evident in the tragic congregations that follow this pernicious doctrine. This is of a piece with the Christian hedonism of his school, (see Christian Hedonism by E S Williams Christian Hedonism?: A biblical examination of John Piper's teaching Amazon link unreliable).
The cross delivers us from sin and into not from purity and holiness, it writes the Law in our hearts and does not in the least efface it. Real disciples love & delight in the heart, spirit and letter of the commandments far more than the scribes and legalists. It is the cherished manifesto of their Lover (Matt. 5.17-19; Jn. 14:15,21; 15.10; Rom. 13.12-14; Gal. 5.21; 1 Jn. 2.2-3; 3.22-24; 5.2-3; 2 Jn. 6; 3 Jn. 11). The Gospel makes us cheerful servants of righteousness, not shifty excusers of sin. It shatters the chains of our depravity, not merely explaining them away. Ultimately the cross serves as a strong barrier to the impenitent fornicator, adulterer or homosexual, thief or extortioner, just as much as it serves as a door to the brokenhearted forsaker of his wickedness, for it removes all our excuses (1 Cor. 6.9-11).
As well as proposing to redefine sin, the estate of the lost, and the character of their hope, it is no wonder the telling original subtitle for this work, since withdrawn, was ‘redefining Christianity.’ This is a heretical and a poisonous book, for all its sweet expression, read it if you must with care, go back often to the prophets, psalms and Gospels to see just how widely it errs. Isaiah predicts the Messiah will 'magnify the law, and make it honourable'.(Isa. 42.21) Mr Keller has done quite the opposite.
Hear Psalm 112, ‘Blessed is the man that fears the LORD, that delights greatly in His commandments.’ Here is the character of real joy and communion.
*(ἀνομία = without law, a key characteristic of enemies of the Lord, 2 Thess. 2.7)