A time travel novel about incest, really, a few years out from Silverberg’s softcore days. Like many “New Wave” SF, sex is pretty prominent than the clean SF of the 1940s-50s.
The interesting thing is that the narrator is named Judson Dan Elliott III, a nod to the Don Elliott/Dan Eliot pen name for Cornith.
The Wikipedia synopsis describes this novel best:
The story’s protagonist is Jud Elliott III, a failed Harvard history masters student in 2059. Bored with his job as a law clerk, he takes up a position with the Time Service as a Time Courier. After an introductory course, Jud shunts up and down the time line (“up the line” is travel into the past; “down the line” is forward time travel, but only to “now-time,” Jud’s present of 2059) as a guide for tourists visiting ancient and medieval Byzantium/Constantinople. Jud’s problems include not only stupid tourists, but also greedy and mentally unstable colleagues who attempt to cause various types of havoc with the past. He is forced to break the rules in order to patch things up without drawing the attention of the Time Patrol. When he meets and falls in love with the ‘marvelous transtemporal paradox called Pulcheria’ – his own multi-great grandmother – Jud succumbs to the lure of the past, creates irreparable paradoxes, and faces the inescapable clutches of the Time Patrol.
Silverberg’s narrative includes some cleverly worked out details about the problems of time-travel tourism. For example, the number of tourists who over the years wish to witness the Sermon on the Mount has increased the audience at the event from the likely dozens to hundreds and even thousands. Time-tour guides re-visiting the same event must also take care not to scan their surroundings too closely, lest they make eye contact with themselves leading another tour party.
Silverberg’s interest in the Byzantine era of Roman history is put to use with a vivid description of Constantinople during the reign of Justinian, and the Nika riots of 532.
The era that Jud Elliott originates from, 2059, seems more like 1969 with a bunch of free-loving hip cats, easy pick ups, getting stoned and having sex parties. But SF often reflects the time it is published.
A lot of interesting time paradoxes are indeed presented, mainly the changing of timelines by seriously altering the past, and the Time Cops who set things straight.
Jud falls in love with his great-great-multi-great grandmother, Pulcheria Ducas, a dark-skinned beauty who marries at age 12. Jud has sex with her when she is 17 — seems her husband cannot give her children (and suggests that Jud may seed his own lineage down the line).
Things go awry when a pedophile gets loose in time. A man in Jud’s tourist group to Byzantium, who has a penchant for little girls, gets his time travel belt device free for his own use and takes off; seems he winds up seducing and marrying Pulcheria at age 11-12, which makes Jud a non-person up the line in 2059, since his lineage never occurred. It is up to Jud and his fellow time couriers to fix this before the Time Cops find out.
In the process, Jud somehow duplicates himself…one of the paradoxes presented is that the couriers must avoid running into and interacting with themselves while “shunting” about.
Seems in 1990-91 there were a series of five books by other writers set in this universe, called “Robert Silverberg’s Time Tours.”
Word has it that Up the Line will soon be republished in an omnibus edition with Project Pendulum and Hawksbill Station, a book to be called 3 x Time.
Hawksbill Station is about political dissidents and criminals sentenced to live in the pre-Cambrian era, and Project Pendulum is a YA-marketed short novel about the first time travelers, a set of twins, and all the time paradoxes they encounter.