The GILH describes a bit more about the background on the selection of Scripture for the Office of Readings and for Mass:
146. The two-year cycle of readings for the liturgy of the hours is so arranged that each year there are readings from nearly all the books of sacred Scripture as well as longer and more difficult texts that are not suitable for inclusion in the Mass. The New Testament as a whole is read each year, partly in the Mass, partly in the liturgy of the hours; but for the Old Testament books a selection has been made of those parts that are of greater importance for the understanding of the history of salvation and for deepening devotion.
The complementarity between the readings in the liturgy of the hours and in the Mass in no way assigns the same texts to the same days or spreads the same books over the same seasons. This would leave the liturgy of the hours with the less important passages and upset the sequence of texts. Rather this complementarity necessarily demands that the same book be used in the Mass and in the liturgy of the hours in alternate years or that, if it is read in the same year, there be some interval in between.