Steve is correct about
RIC II being the definitive book about
Flavian coinage. I would also like to add Coins of the
Roman Empire in the British Museum II:
Vespasian to
Domitian (
BMCRE II). While the new
RIC is a more thorough and accurate
catalog, the
BMCRE has a lot of interpretive information about coin
types not found anywhere else.
I am also of the opinion you cannot divorce the
history from the coinage. Here are a few books that are fundamental in understanding the
Flavian era:
Vespasian by Barbara Levick, The Emperor
Titus by Brian
Jones, The Emperor
Domitian by Brian
Jones, Suetonius: the
Flavian Emperors by Brian
Jones.
If you are on a tight
budget and wish to purchase a fairly inexpensive volume about the coinage of the era,
Roman Silver Coins II:
Tiberius to
Commodus covers the period you are interested in. There isn't much in the way of text, but it does list most of the silver coins minted by each reign.