The Eagle in the Snow and Friend of Caesar and The Nineth Legion.
Maybe favourites is more applicable in my case.
My great-niece started reading Friend of Caesar (by Stearns, written about 1900). she said she has a hard time putting it down. She is 16, about the same age I was when I first read it. It is kind of nice to see one very young enjoy a book that I love.
The Roman Republic by Michael Crawford and As the Romans Did by Jo-Ann Shelton (I know a source book, I love reading all the quotes). When I first read the Crawford book, it had many aha moments... someone felt the same way about the Roman republic as I did and (big point) he knew history to back up his points!