The generic, so to speak, monastic breviary in the Benedictine Tradition is the one I linked above. Secondly, if you do join a monastery, you will most certainly be praying their version, but the Monastic Diurnal would give you a solid background in the tradition of praying the office as the monks do. You may also wish to consider reading the Holy Rule of St. Benedict along with a good commentary (I can recommend some if you are interested). The Patriarch spends a large part of the Rule discussing the manner in which the office is to be compiled and prayed. However, since the Abbot takes the place of Christ in the monastery, St. Benedict gives the him the flexibility to structure the office as he sees fit. Therefore, the monks pray whatever form of the office the abbot decides is proper for his community.
Peace,
The Monastic Diurnal is “generic” but the links given are the pre-Vatican II Monastic Office. The current Monastic Office follows the current liturgical calendar and allows the psalms of Prime to be redistributed into other hours with a couple of different options.
For the post-Vatican II Monastic breviary the “official” version is the Monastic Antiphonary put out by Solesmes starting in 2005, in 5 volumes. Presently only 4 are available, Vigils is still not complete, for that the 1980 Psalterium Monasticum can be used. These are published by Solesmes and all are available from there.
In addition there are 3 additional approved schemas for general use post-Vatican II:
Schema B consists of all 150 psalms on a one-week cycle though with a couple of options to spread them over 2 weeks;
Schema C says the psalter over 2 weeks;
Schema D says the psalter over 2 weeks.
The layout for those schemas can be found in the 1980 Psalterium Monasticum or Psautier Monastique (Latin-French). However much page flipping would be required. Schema B is also shared with the Cistercians. A French-only version has been published. The abbey I am associated with uses this schema, as do I occasionally when I’m not too busy (otherwise I use the 4-week current LOTH).
Many abbeys have their own schemas. The abbot has considerable latitude in this regard as you pointed out. Douai abbey in the UK for instance has a schema that has Matins (Vigils & Lauds combined) and the mid-day office on a 4-week schema very similar to the LOTH and chanted in English, with the 1934 Monastic Antiphonary with Vespers and Compline on a 1-week cycle chanted in Latin. I liked this schema very much, a mix of modern and traditional.
The vast majority of monasteries will use a post-Vatican II breviary, so the Monastic Diurnal would not fit. Even those using the traditional Benedictine Office (Schema A, like the Diurnal but with the psalms of Prime redistributed and the modern calendar), will use the post-Vatican II version. This has exactly the same liturgical year and collects as the LOTH; the Benedictine calendar is proper but is kept up to date with modern saints like the Roman calendar.
Monasteries where the Diurnal would be appropriate would be those using the EF; Clear Creek in the US, Barroux and Fontgombault in France to name a couple.
For laity, the 4-volume LOTH seems to make the most sense for busy folks. If you follow the EF Mass then the 1960 Roman Breviary would work as would the Diurnal, but they’re both a much heavier load and moreover the 1960 Roman Breviary is not at all “traditional”, it is a relatively modern Office dating back only to 1910. The Diurnal (and current Monastic Schema A) are the true “traditional” offices as their basic layout was spelled out by St Benedict himself in his Rule, approximately 1500 years ago. Vigils in the Monastic Office, takes a full hour or more if chanted, and even recited, will probably take close to 40 minutes as there are 12 psalms. As an Oblate, I find Vigils too important to pass up due to the patristic readings and the “night watch” character of the hour; I use the Office of Readings for Vigils which I recite usually at about 5:30 am on weekdays these days.
Many people disparage the current 4-weel LOTH but it really isn’t that awful and it certainly takes considerable care to consider tradition in the Divine Office, or to at least allow options that do. Moreover there are now many interesting versions of it in chant notation both in Latin, French or English, for those inclined to chant it. It’s worth a serious look.