I've seen it referred to here, and I've seen it at two different book stores this past week. I took a peek and saw some random prayers (as in, not organized for a particular time or activity), but is there more to it than this?
The Book of Common Prayer is akin to the Roman Missal, Breviary, and Ritual all wrapped into one. When Anglicanism came about as we know it today, Thomas Cranmer wanted to make only two books necessary to be an Anglican - the Bible, and the Prayer Book. The Prayer Book has the order for the Daily Office, the Litany, the Collects for the whole year, the order for Holy Communion, the order for Baptism, Confirmation, Marriage, and Burials, as well as Ordinations. It also has a small catechism and the creedal statement of Anglicanism if you will, the 39 Articles. It doubles as a service book for clergy and a devotion for laity. The classic adage is lex orandi, lex credendi, aka We believe what we pray. More than anything else, the Prayer Book is Anglicanism. It defines it, and it gives substance to the considerations of theologians and scholars and tradition.
And there is quite a difference between these modern versions and older versions. In the USA, with which I am unfamiliar, there was a massive break between the 28 and the 79 texts for Holy Communion. This is major, because, they retained their changes under the same name of "Common Prayer." The Canadians got away with it, a bit, as they didn't change their Common Prayer but rather published the Book of Alternative Services which the majority of Anglican parishes use for the Sunday service. It is very similar to the modern English Missale Romanum before the revision of 2011. Various Eucharistic prayers, all of 'divers' churchmanship. The Church of England, likewise, got away with a new liturgy with the publication of the Book of Common Worship - the liturgy also almost identical to that which was found in Alternative Services, which contained contemporary and traditional language versions. The 1962 prayerbook in Canada is most like the 1662 prayerbook. Many people argue that the liturgical revolution began during Vatican II rippled throughout the further branches of the Catholic Church. Thus it reached Anglicanism quite quickly, and these particular Churches began to catch the wind and attempt to 'reform' in a way, evidenced in the various experimental liturgies produced in the late 60's and early 70's throughout the Anglican Communion. Don't confuse the Book of Common Prayer with Common Prayer: A Liturgy for Ordinary Radicals, a completely separate text.
It is basically all public Anglican prayers rolled into one... the Rite of Holy Communion, the daily Offices, the Rites of Marriage, the Ordinal, and others. It was written by the Bishops and Archbishops over the course of the 1500s and 1600s, the final form in 1662, remaining with minor alterations from then until this past century, the 1960s... after Vatican 2 our leaders became possessed with liturgical innovations of our own, and the resulting Episcopalian Book of Prayer of 1979 was full of grievous errors, a decisive break with the Anglican liturgical tradition... Thankfully the new ACNA rites are largely based on the older tradition, so we are making a return to the authentic Anglicanism