See this online ebook:

  • Manual of the Forty Hours’ Adoration for the Catholic Laity (Brooklyn, N.Y.: International Catholic Truth Society). With Ecclesiastical Authority. May be read online, and available in pdf, epub, mobi, and other formats, at Internet Archive. [N.B., No date, but we surmise it was printed within the lifetime of the International Catholic Truth Society, which according to CatholicSaints.info was 1899–1924, and that it is therefore in the public domain. Advice on the matter would be appreciated.]

See also these related ebooks:

  • The Adoration of the Blessed Sacrament, by Rev. A. [Albert] Tesnière [1847-19090, Anne R. Bennett Gladstone (New York, Cincinnati, Chicago: Benziger Brothers, 1902). With Imprimatur. May be read online, and available in pdf, epub, mobi, and other formats, at Internet Archive.
  • Calvary and the Altar; or, Devotions for the Octave of the Blessed Sacrament, the Forty Hours (Quarant’ ore) and the Days of Perpetual Adoration, by Mademoiselle [Léonie] Guillemaut; translated and with a preface by Lady Herbert [Mary Elizabeth Herbert, Baroness] (London, Dublin, Derby: Thomas Richardson and Son; New York: Henry H. Richardson & Co., 1870). Available in pdf, mobi/kindle, epub, and other formats at Internet Archive.
  • The Eucharistic Christ: Reflections and Considerations on the Blessed Sacrament, by Rev. A. [Albert] Tesnière [1847-19090], translated by Anne R. Bennett Gladstone, with a Preface by Rev. D.J. McMahon, D.D. (New York, Cincinnati, Chicago: Benziger Brothers, 1897). With Imprimatur. May be read online, and available in pdf, epub, mobi, and other formats, at Internet Archive.
  • He is Calling Me: Helps in Visiting the Blessed Sacrament, by Matthew Russell, S.J. [1834-1912] (London: Burns & Oates, 1912). With Imprimatur. May be read online, and available in pdf, epub, mobi, and other formats, at Internet Archive.
  • The History of Eucharistic Adoration Development of Doctrine in the Catholic Church, by John A. Hardon, S.J. Available in pdf format (on this page) of the Real Presence Eucharistic Education and Adoration Association; and may be read online (on this page) of the EWTN Libraries.
  • Jesus is Waiting: Appeals and Reproaches from the Prisoner of Love, by  Matthew Russell, S.J. [1834-1912] (London: Burns & Oates; New York: Benziger Brothers, 1911). With Imprimatur. May be read online, and available in pdf, epub, mobi, and other formats, at Internet Archive.
  • Moments Before the Tabernacle, by Rev. Matthew Russell, S.J. [1834-1912] (New York, Cincinnati, Chicago: Benziger Brothers, 1893). With Imprimatur. May be read online, and available in pdf, epub, mobi, and other formats, at Internet Archive.
  • Perpetual Eucharistic Adoration [Manual], by the Real Presence Association (Lombard, Illinois: Real Presence Eucharistic Education and Adoration Association, 2001-2011). Contains various materials on perpetual adoration, which are available as one combined file and as individual files through this page of the Real Presence Eucharistic Education and Adoration Association. The combined pdf file is also available on this page at Pray and Fast for America.
  • Visits to the Most Holy Sacrament, etc., for Every Day in the Month; Aspirations of Love to Jesus in the Holy Eucharist; Rules for Frequent Communion, with a Defence of the Same; Meditations for Every Day in the Week; and a Novena for All Soul’s Day, by St. Alphonsus M. Liguori, translated by a Catholic clergyman, to which is added A Methods of Devoutly Hearing Mass” by Blessed Leonard a Porto Mauritio (New York: Catholic Publication Society, [1870]). May be read online, and available in pdf, epub, mobi, and other formats, at Internet Archive and Open Library; and available in pdf format at Today’s Catholic World.

On the Feast of Saint Anthony Maria Zaccaria. For other online texts and legally free ebooks, you may access the List of Free eBooks (Arranged by Title) and the List of Free eBooks (Grouped by Subject).