The title of Book Five is “These are the generations of Shem” (Gen 11:10). It is considerably shorter than any book we have seen and it is missing the poetry and epilogue. The text is in a hurry to get to Abram.
The royal genealogy follows the pattern we saw in the royal genealogy of Book Two, with one major departure: it is missing the summary/death statement for each: ‘Thus all the days of ____ were ___ years, and he died.” The only significance it seems appropriate to conclude from this omission is that the pattern has been shortened to get to Abram. Especially since this summary/death statement is used in the next book for Terah in order to focus on Abram.
A second difference with the royal genealogy of Book Two is that in Book Five there is no significance attributed to number seven. In Book Two there was a departure from the pattern to highlight Enoch, but there is no such departure from the pattern for Serug. Again the brevity does not tell us whether number seven was just simply not noteworthy or anything about him, but it does reinforce this picture of wanting to move quickly to Abram.
A third difference with the royal genealogy of Book Two and the other genealogies is that the three sons usually belong to the plus one generation. For the evil Lamech in Book One, number seven in that genealogy, the eighth generation had three sons. For Noah in Book Two, number ten in that genealogy, the eleventh generation had three sons. But here the tenth generation is the one with the three sons: Abram, Nahor, and Haran. The LXX adds Cainan as the son of Arpachshad and father of Shelah. But this addition to the last book would have made seventy-one nations rather than seventy and here would highlight Terah rather than Abram. Book Five wants to highlight Abram as having come in the fullness (ten) of time.
The lifespans are considerably shorter in Book Five compared to Book Two, suggesting that life is more difficult post-flood. I am unaware of any other significance to these numbers. This may be significant in and of itself.
This royal genealogy, like that of Book Two (which ignores the Cain and Abel story), tells us the legitimate heirs of the promise. It does not tell us about Peleg’s non-elect brother Joktan mentioned in the last book. All of the focus is on the heirs to the promise. But Scripture as a whole does not speak too favorably of the generations leading up to Abraham who came in the fullness of time. Joshua tells us, “Long ago, your fathers lived beyond the Euphrates, Terah, the father of Abraham and of Nahor; and they served other gods” (Joshua 24:2).
The next book will begin with some recapitulation and adds Lot: “Now these are the generations of Terah. Terah fathered Abram, Nahor, and Haran; and Haran fathered Lot” (Gen 11:27) and does include the summary/death statement for Terah, “The days of Terah were 205 years, and Terah died in Haran” (Gen 11:32) so that the book can focus on Abram, Nahor, and Lot.
Thus in the fullness of time, came Abram, Nahor and Haran. Now we will see God choose Abram to bless.