The two latest books available as both e-books and print books on the subject are:

Interpreting Ground-penetrating Radar for Archaeology (2012: Left Coast Press)

You can order it here: 

http://www.lcoastpress.com/book.php?id=415

Ground-penetrating Radar for Archaeology, 3rd Edition (2013)  Alta Mira Press Rowman and Littlefield

You can order it here:

https://rowman.com/ISBN/978-0-7591-2350-2

 

The first book on the subject: Conyers and Goodman (1998) was translated into Italian (re-titled Ground Penetrating Radar: Un'introduzione per gli archeologi), it is now available from Aracne editrice in Rome. It was translated by Giovanni Leucci, who knows GPR well, and I hear from my Italian friends that it is quite readable.

You can download it here:

http://www.aracneeditrice.it/pdf/9788854809512.pdf