There are 3 books in the Sierra Waters series. The newest book is Chronica which came out in 2017.

1
The Plot to Save Socrates

Book cover of The Plot to Save Socrates
Paul Levinson's astonishing science fiction novel is a surprise and a delight: In the year 2042, Sierra, a young graduate student in Classics, is shown a new dialog of Socrates, recently discovered, in which a time traveler tries to argue that Socrates might escape death by travel to the future!…
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2
Unburning Alexandria

Book cover of Unburning Alexandria
Mid-twenty-first century time traveler Sierra Waters, fresh from her mission to save Socrates from the hemlock, is determined to alter history yet again, by saving the ancient Library of Alexandria - where as many as 750,000 one-of-a-kind texts were lost, an event described by many as "one of the greatest…

3
Chronica

Book cover of Chronica
Sierra and Max arrive in 2062, and find the world has somewhat changed. Joe Biden was President from 2009-2017, and train travel is much more prominent. Was this due to the scrolls that she rescued from the Library of Alexandria? Heron's Chronica, which describes how to build a time travel…