A friend of mine asked about book recommendations for Northern Gaul. I pulled together a brief bibliography and sent it to her. I’m also including it here in case other people find it useful.
Cunliffe, B. W. (1988) Greeks, Romans, and barbarians : Spheres of interaction. New York, Methuen. ISBN 0416019919
Derks, Ton. (1998) Gods, Temples and Religious Practices: The Transformation of Religious Ideas and Values in Roman Gaul. Amsterdam Archaeological Studies 2. Amsterdam: Amsterdam University Press, 1998. Pp. x, 325. ISBN 90-5356-254-0. F85/$39.50.
Review: http://ccat.sas.upenn.edu/bmcr/1999/1999-10-34.html
Green, M. (1996) The Celtic World. Routledge. Searchable content on Amazon: http://www.amazon.com/Celtic-World-Miranda-Green
Hamilton, E. G. (1996) Technology and Social Change in Belgic Gaul. Museum Applied Science Center for Archaeology/Pennsylvania Museum of Archaeology and Anthropology
http://www.oxbowbooks.com/bookinfo.cfm/ID/50293
Macready, S. (1983) Cross-Channel Trade between Gaul and Britain in the pre-Roman Iron Age. London: Society of Antiquaries of London. 232p, 89 illus, 21 figs ISBN-13: 978-0-85431-239-9 ISBN-10: 0-85431-239-0
Roymans, N., editor From the Sword to the Plough: Three Studies on the Earliest Romanisation of Northern Gaul. Distributed for Amsterdam University Press. 260 p. 8-3/4 x 12 1996 Series: (A-AAS) Amsterdam University Press – Amsterdam Archaeological Studies
http://www.press.uchicago.edu/cgi-bin/hfs.cgi/00/15545.ctl
Google books preview: http://books.google.com/books?id=6faemfaETroC&dq=northern+gaul&printsec=frontcover&source=web&ots=Kd5rkO1r1e&sig=bIHq7JAnLj5sYT4P4RChzohY4U0#PPA1,M1
Watson, A. (2007?) Religious Acculturation and Assimilation in Belgic Gaul and Aquitania from the Roman Conquest until the end of the Second Century CE. ISBN-13: 978-1-4073-0036-8 ISBN-10: 1-4073-0036-9 http://www.oxbowbooks.com/bookinfo.cfm/ID/81039
Wells, P. S. (1999) The Barbarians Speak: how the conquered peoples shaped Roman Europe. Princeton, N.J., Princeton University Press. ISBN 0691058717
Wells, P. S. (2001) Beyond Celts, Germans and Scythians: Archaeology and Identity in Iron Age Europe. Duckworth Publishers. Searchable content on Amazon: http://www.amazon.com/Beyond-Celts-Germans-Scythians-Archaeology
Beyond Celts, Germans and Scythians: Archaeology and Identity in Iron Age Europe (Duckworth Debates in Archaeology) (Duckworth Debates in Archaeology) by Peter S. Wells (Paperback – Aug 20, 2001)
Woolf, G. (1998) Becoming Roman : the origins of provincial civilization in Gaul. Cambridge, Cambridge University Press. ISBN 0521414458 (hardback) 0521789826 (paperback)
This site (compiled by Ton Derks) has some excellent links:
http://www.unc.edu/awmc/toc.html
French resources
Bedon, R. (1999) Les villes des trois Gaules, de César à Néron Paris, Picard. ISBN 2-7084-0563-2
Chevallier, Raymond (1998) Voyages et Déplacements dans l’Empire Romain. Paris, Armand Collin. ISBN 2200371497
Espérandieu, É. (1907) Recueil général des bas-reliefs de la Gaule romaine. Paris, Imprimerie Nationale.
Faudet, I. (1993) Les Temples de Tradition Celtique en Gaule Romaine Paris, Editions Errance. ISBN 2877720748