Here are the books I have written (and co-written) on GPR, which are available at the sites below. Some of the earlier editions to books I have left out, as they are now obsolete:
Ground-penetrating Radar for Archaeology, 4th edition

This book has been completely revised and added to, making it very different from its 3rd edition (2013). It contains all new figures, updated sections on many of the recent GPR technologies, and many new ideas on where this field has gone in the last 10 years and where it is going. I spent some time going back through many of my surveys during the last 20 years and discussed some interesting ways that my ideas have changed over that time and what I have learned about radar, the ground, and data processing and interpretation. I hope it is fun to read, and interesting to those of you who work with GPR in archaeology but also other fields.
Georadar Aplicado en Geotecnia y Arqueología:
In November, 2021 I published a book written with co-author Adolfo Martinez from Monterrey, Mexico. We collaborated on this so that it can be about both archaeology and geotechnical applications. Adolfo is the magician who make this all work in Spanish. We also produced a Spanish glossary in the back for the technical GPR words in Spanish (some of which we have invented ourselves).

Ground-penetrating Radar and Magnetometry for Buried Landscape Analysis

In this book I use many examples from around the world on how these geophysical tools can be used together to understand complex buried archaeological sites.
Ground-penetrating Radar for Geoarchaeology

Here there are many examples and methods on how to apply GPR to complex geological situations, with sedimentary environments categorized and various soil types and stratigraphic conditions.
Interpreting Ground-penetrating Radar for Archaeology

I spent a good amount of time writing this book to show what can be done with GPR data. My thought was that people needed to know much more than just how to collect and process data, to produce interesting images. They need to know what to do with it when they are finished with the processing. So, this book is all about that type of interpretative analysis, which is also important to do within the string of data processing steps.
Ground-penetrating Radar for Archaeology, First Edition (Conyers and Goodman 1998). This is first book on the subject of GPR is out of press in English (and outdated too!): Conyers and Goodman (1998).

It can still be bought used here
Ground-penetrating Radar: Un’introduzione per glib archeologi
translated into Italian by Giovanni Leucci, who knows GPR well

Available from Aracne Editrice in Rome. It was translated. I hear from my Italian friends that it is quite readable.