The Office has been drawn up and arranged in such a way that not only clergy but also religious and indeed laity may participate in it, since it is the prayer of the whole people of God.
I quoted this from Pope Paul VI's Apostolic Constitution on the Liturgy of the Hours in a 10/10 post about the instructions on the Vatican II revision of the breviary. But it wasn't until last week that I really appreciated what the Second Vatican council did for us lay folk in giving us a short, vernacular breviary.
The reason for this is that I recently downloaded a book on Kindle (it was a freebie, originally from Gutenberg or Googlebooks), titled The Divine Office by a Father Edward Quigley, copyright 1920. It's basically a guide to the pre-Vatican II breviary, written for priests. It's packed with historical information for the liturgy geek.
There's also a rather scary section on all the ways a priest could sin (either mortally or venially) by not saying the full office correctly every single day. And in those days you prayed all 150 psalms every week, rather than every month. So the hours of the liturgy were roughly four times as long as they are now.
And they were all in Latin. And apparently reading a vernacular translation did not "count" as praying the official prayer of the Church. Any lay person who did this was engaging in a devotion, not participating in the liturgy.
So, although I'm a fairly traditional Catholic and enjoy hearing mass in Latin and singing Gregorian chant, I am really, really happy about the Vatican II breviary. As things stand now, it is fairly doable to read the liturgy in the 10 minute chunks (give or take) it now comes in. (And fifteen to twenty most days for Office of Readings). A quick look at an online Breviarum Romanum shows five psalms each for lauds and vespers. That could easily put me over the edge into thinking: this is just too much, had the Divine Office of today remained what it was before the Council. That, and the fact that my Latin is too little to pray well in that language.
In addition, the complete office back then had 8 mandatory liturgical hours, whereas today it's 5. (Not that laity are ever obliged to do the whole thing, but if doing the complete office is one's goal, then it's a whole lot easier with only 5 liturgical hours.)
Reading between the lines in Fr. Quigley's text, one gets the definite impression that length of the old Divine Office was a burden to many a parish priest. There were all kinds of moral theology regulations for what bare minimum a priest could get away with to fulfill his breviary obligation. It appears that a priest might often have to just say a whole day's office in one block of time, murmuring it as quickly as possible with little reflection on the psalms, just to get it done. Quigley even refers to the "difficult work" of trying to pray office fervently.
Admittedly I haven't made a lengthy study of the old breviary, and I am NOT trying to criticize it or be a "chronological snob" who thinks that everything post-Vatican II is better just because it is newer. On the contrary, having passed my childhood (1960s and 70s) arguing with modernist religion teachers who continually contradicted the Baltimore catechism my parents had me study at home, I know first hand of the sorry misapplication of Vatican II directives.
But if it weren't for Vatican II, I and many thousands more would have missed out on the beauty and consolation of praying the psalms in rhythm with the liturgical year and in harmony with the Church universal.