On May 21, 1900, Ellen White wrote: 4BIO 393.2
God would be pleased to see The Desire of Ages in every home. In this book is contained the light He has given upon His Word. To our canvassers I would say, “Go forth with your hearts softened and subdued by reading of the life of Christ. Drink deeply of the water of salvation, that it may be in your heart as a living spring, flowing forth to refresh souls ready to perish.”—Letter 75, 1900.
Looking back in 1906, Ellen White freely attributed the truths set forth in the books tracing the great-controversy story to the work of the Holy Spirit. She mentioned only three of the Conflict books, for Prophets and Kings and The Acts of the Apostles were not yet published. 4BIO 393.3
How many have read carefully Patriarchs and Prophets, The Great Controversy, and The Desire of Ages? I wish all to understand that my confidence in the light that God has given stands firm, because I know that the Holy Spirit's power magnified the truth, and made it honorable, saying: “This is the way, walk ye in it.” In my books, the truth is stated, barricaded by a “Thus saith the Lord.” 4BIO 393.4
The Holy Spirit traced these truths upon my heart and mind as indelibly as the law was traced by the finger of God, upon the tables of stone, which are now in the ark.—Letter 90, 1906 (Colporteur Ministry, 126). 4BIO 393.5