In addition to the reading of Scripture at the Daily Office there is a long tradition of the lives of the saints and other non-Scriptural readings being used, particularly at the monastic Office of Vigils. On Sundays and significant feasts a commentary on the Gospel was often read in addition to other readings. For more on modern sources for such readings see my former post here, of which the following sections are extracted and adapted focussing on the use of such readings with Common Worship: Daily Prayer. In the monastic tradition the readings are generally linked closely to the Scripture passage just read. The resources listed below (with the exception of the commentaries on the Gospel passages) are not linked in this way. I have long fantasised about indexing the various collections of readings to the passages of Scripture in the CW:DP lectionary. But life is too short.
I hope that the resources listed will be helpful in enriching the Daily Office. The readings from Anglican tradition are particularly rich and many Anglicans are woefully ignorant of our own tradition. I particularly recommend them. Kenneth Stevenson was my bishop in Portsmouth and his Love’s Redeeming Work (produced with Geoffrey Rowell) should be an essential companion for all in leadership in our churches (it is now available on Kindle as well as in print) together with the dated 
but superb Anglicanism (More and Cross).
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Anglican lectionaries for the Daily Office have traditionally consisted of four readings each day. When the Joint Liturgical Group produced a Daily Office (in 1969 originally and a revised version in 1978) the lectionary had three readings each day over a two year period. It was at this time that Christopher Campling produced his two volume, two year cycle of non-Scriptural readings The Fourth Lesson, DLT 1974. It provides a series of readings many from Anglican and most from modern sources, these normally extend in a sequence over several days which is sometimes a relief from the stand-alone chunks provided in other sources. Sadly it is no longer in print but copies are often available second-hand.
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For saints days Anglicans will wish to use Celebrating the Saints, Canterbury Press. This provides readings for all entries on the Calendars of the Church of England, Scottish Episcopal Church, Church of Ireland and Church in Wales.
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For Sundays Celebrating Sundays provides non-Scriptural readings geared to the Sunday Gospels, originally designed for use at the monastic vigil Office when the Gospel is read – a resource created by Fr Stephen Holmes when he was Prior of Pluscarden Abbey (he is now a priest in the Church of England). This volume contains all the adaptations needed for the Revised Common lectionary.
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The English Benedictines produced a three volume set of readings on the Sunday Gospels called Christ Our Light in 1979, and later republished as Journey with the Fathers, New City Press 1994. A further three volume set Meditations on the Sunday Gospels edited by Augustinian John Rotelle (New City 1995) has second readings from mainly non-Patristic Sources including twentieth-century authors. Rotelle also edited Augustine on the Sunday Gospels (Augustinian Press, 1998 ) another extremely useful source which I go to every week for sermon preparation and often for my daily lectio. All of these resources are geared to the original form of the Sunday Mass lectionary and so need some adaptation for the RCL, but they are well indexed.
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Celebrating the Seasons is an excellent one year cycle of non-Scriptural readings for the Office with many texts from Anglican sources and edited by the now bishop of Exeter, Robert Atwell. Prayer Book Spirituality, Church Hymnal Corporation 1989, ed. J. Robert Wright, has a great series of readings in the Anglican tradition, many of which are suitable for reading aloud. The much neglected Anglicanism, SPCK 1935, ed. Paul Elmer More and Frank Leslie Cross can be mined for readings, as can Kenneth Stevenson’s magnificent Love’s Redeeming Work.
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In Ordinary Time, in particular, reading a commentary on one of the psalms that have been prayed at the Office can be very effective. In John Eaton’s The Psalms (Continuum, 2005) the final section of commentary on each psalm works well. Michael Sadgrove’s commentary on the Evening psalms in the Prayer Book cycle, I Will Trust In You (SPCK 2009) also provides good material. I like Gregory Polan’s introductions to each psalm in The Psalms: Songs of Faith and Praise (Paulist, 2014). It is out of print now but David Durston’s A Light On My Path (Canterbury Press, 2002) is excellent and a direct commentary on the CW psalter. I am also really enjoying Reflections on the Psalms, Church House 2015.
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The Customary of the Ordinariate of Our Lady of Walsingham also has a large number of readings designed for use at the Daily Office for many celebrations of saints and most Sundays and Festivals in the seasons. The readings are sometimes a little long and often rather dense, Victorian Anglo-Catholic prose but well worth using.
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Finally, if you don’t know The Glenstal Book of Readings for the Seasons, it is available on Amazon in print or Kindle form. It is an excellent additional resource, mainly for more contemporary non-Scriptural readings. They are linked to the one-year cycle of the Roman Catholic Divine Office, but not too tightly. I wondered at first if they would wear thin but the readings are of such depth that they last well.
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With its already rich diet of four readings adding a fifth reading might seem like hard work. But the suggestion in CW:DP for making the ‘Prayer During the Day‘ provision a sort of extended Office of Readings is good one. It would be possible to use one Scriptural and one non-Scriptural reading at this. Some Anglicans use the permission given to use the Daily Eucharistic Lectionary at the Office, but this needs the Scriptural reading from the Office of Readings (ideally in the two year cycle) to really provide adequate coverage of the Bible.
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In my own recent practice I find two long readings in the middle of the day unsustainable, I am often rushing between meetings. So I am using three readings at the Morning Office which is the time when it is easiest to sustain a longer period of prayer. I have begun experimenting with adding the Gospel of the following day, the Patristic commentary (in one of the sources above) and the Te Deum to Evening Prayer on a Saturday. It is early days but that seems to work.
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