The Little Office seems to be making a comeback, I'm glad to say.
Amusingly, it is if anything slightly longer than the present-day Divine Office! (A friend of mine acidly refers to the latter as "the Little Office of Vatican II" - but don't get me wrong, I used the modern Liturgy of the Hours for over a decade with much profit.)
Why, then, is it termed the "Little" Office? Well, for a start, it is in large part invariable, as opposed to having many changeable texts.
In place of the nine psalms of Matins in the Breviary, it takes the three Nocturns of Matins of the Common of feasts of the Blessed Virgin, and ordains that only one Nocturn, that is, three psalms, shall be said each day. This is the biggest difference between the Little Office and the Daily Office. Now, on average, Matins in the Breviary has 115 psalm-verses (exclusive of the Invitatory Psalm), and Matins for feasts of Our Lady has 108, so that there is virtually no difference in length until it is realized that only one-third of this is read on any given day in the Little Office, so Matins therein has only 36 psalm-verses on average. I must say that praying one's way through nine psalms is no joke, and that three only is a real relief.
As for the lessons at Matins in the Little Office, well, they are taken from Ecclesiasticus xxiv; now, during the fifth week of August the Breviary takes its Matins Lessons from Ecclesiasticus, and on average reads 16 verses of a chapter each day. The Little Office only reads the whole or part of nine verses of Scripture (Ecclus xxiv, 11b-13 then 15b-16 and 17-20) in its three Lessons, except in Advent and on the 25th of March, when it reads the thirteen verses of the Gospel of the Annunciation (St Luke i, 26-38). Thus it is that the Lessons read are shorter than their counterparts in the Breviary, perhaps even 50% shorter. Otherwise, Matins has the same structure and contents in both forms of the Hours.
Lauds in the Little Office is identical in psalmody of Sunday in the Breviary (Psalms 92, 99 and 62, the Benedicite from Daniel iii, and Psalm 148), since for all feasts, including Marian ones, the Sunday psalms are used: and the tally of 56 psalm-verses is virtually that of the daily Office at Lauds (which has 58 on average). The structure of Lauds is otherwise preserved exactly as in the Breviary, just as one would expect for a feast of Our Lady. Here it is well to note that until the reforms under St Pius X, three more psalms were read at Lauds: Psalm 66 was added to Psalm 62 under one Gloria Patri, and Psalms 149 and 150 were likewise added to Psalm 150 - indeed, these three last were used daily at Lauds, and gave it its very name from their continual repetition of Laudate. These three psalms had an additional 20 psalm-verses, but they were deleted from the Little Office also, presumably to keep it closely parallel to the main Office as in the Breviary, lest the Little be longer!
The Little Hours (in this usage, Prime, Terce, Sext, None and also Compline) are about the same in structure in both the Daily and the Little Office, to a first approximation, but remembering always that Prime de Beata (of Our Lady) lacks the so-called chapter office, that is, the second part of Prime also named after its versicle Pretiosa., and likewise Compline de Beata lacks the prefatory officium collationis, which is the short reading (I St Peter v, 8-9) then Confiteor and so forth acting as a penitential rite. (There would be nothing to stop someone prepending and appending these if they desired and had the relevant texts, of course; if ever the Breviary and the Little Office are read together, one reads Prime down to before Pretiosa, then inserts Prime of the Blessed Virgin, then the Martyrology if used, and then continues with Pretiosa and the succeeding prayers.) However, none of the Marian versions of the Little Hours contains a short responsory (though they do in the Dominican Rite Little Office, of which more anon), and, in a curious parallel to the Benedictine Rite, Compline of Our Lady has no antiphon for the psalms (again, the Dominican version does have one). Furthermore, the number of psalm-verses read at the Little Hours of the Little Office is as one would expect less than those read on average at the Little Hours in the great or ordinary Office:
- Prime of Our Lady has 23 psalm-verses, as opposed to 40 on average in the Breviary;
- Terce of Our Lady also has 23 psalm-verses, as opposed to 32 on average in the Breviary;
- Sext of Our Lady has 18 psalm-verses, as opposed to again 32 on average in the Breviary;
- None of Our Lady has 21 psalm-verses, as opposed to 36 on average in the Breviary;
- Compline of Our Lady has 20 psalm-verses, as opposed to 32 on average in the Breviary.
It will be seen that these Little Hours de Beata have in aggregate 105 psalm-verses, the equivalent in the Breviary, 172 - so the former is only about 60% of the latter in length.
Finally, Vespers: in the Little Office, the Vespers provided is the same as Vespers for a Marian feast in the Breviary, and so has 40 psalm-verses, as opposed to the 47 or so that occur on average each ferial day in the main Office.
In sum, the psalmody of Our Lady's Office has about 237 verses each day, while one reading the psalms of the Roman Breviary gets through an average of 392: so the Little Office is only 60% of the Daily Office in length - hence its name. Even if (as pro pia devotione one could augment the appointed Nocturn at Matins with the other two) there were all nine psalms read daily at Matins of the Blessed Virgin, the total would still fall short of the Breviary and have only 309 psalm-verses, about 80% of the latter's tally. (And the three former psalms at Lauds make little difference if included also.)
While beyond the scope of what I've written here, it is noteworthy that the older religious orders had their own recensions of the Little Office; the Carthusians still retain in use the Office of the Blessed Virgin Mary, which is certainly not "Little" - containing all the pre-Pius X psalmody of Lauds, and at Prime through to None praying first Psalm 53, then all of Psalm 118! Their Marian Compline, too, is longer, being the same length as ordinary Compline.
Indeed, all the dioceses of mediæval Europe had varying local forms of Our Lady's Hours...