The immediate influence of the book was considerable.
Dr. Samuel Johnson said (Boswell's LIFE OF JOHNSON, ch. 1): "I became a sort of lax talker against religion, for I did not think much against it; and this lasted until I went to Oxford, where it would not be suffered. When at Oxford, I took up Law's SERIOUS CALL, expecting to find it a dull book (as such books generally are), and perhaps to laugh at it. But I found Law quite an overmatch for me; and this was the first occasion of my thinking in earnest of religion after I became capable of rational inquiry."
Gibbon (as mentioned above) said: "If Mr. Law finds a spark of piety in a reader's mind, he will soon kindle it into a flame."
John Wesley calls it one of three books which accounted for his first "explicit resolve to be all devoted to God." Later, when denying, in response to a question, that Methodism was founded on Law's writings, he added that "Methodists carefully read these books and were greatly profitted by them." In 1744 he published extracts from the SERIOUS CALL, thereby introducing it to a wider audience than it already had. About eighteen months before his death, he called it "a treatise which will hardly be excelled, if it be equalled, either for beauty of expression or for depth of thought."
Charles Wesley, George Whitefield, Henry Venn, William Wilberforce, and Thomas Scott each described reading the book as a major turning-point in his life. All in all, there were few leaders of the English Evangelical movement on whom it did not have a profound influence.
Some Christians have considered Law's work inadequate, as not sufficiently concerned with Justification by Faith, to which objection Law would doubtless have replied: "But I never offered it as a complete presentation of the Gospel, only as a reminder of the words, 'Go and sin no more,' which are surely a part of the Gospel."
Law's SERIOUS CALL and his THE SPIRIT OF LOVE are currently available for $10 in a single volume (527 pages) in the series CLASSICS OF WESTERN SPIRITUALITY, published by the Paulist Press.