Oxford Classical Dictionary, Main DE 5 .O9 2003
Oxford Companion to Classical Civilization, Main DE 5 .O92 1998
Late Antiquity, a Guide to the Postclassical World, Main DE 5 .L29 1999. Has chapters on religious communities, the good life, habitat, among others. This is followed by a dictionary portion with both topical and biographical entries. Late antiquity is the period roughly 250-850 A.D.
Ancient Europe 8000 B.C. - 1000 A.D.: Encyclopedia of the Barbarian World, Reference D 62 .A52 2004 v. 1-2
V. 1 covers Mesolithic to Copper Ages, c8000-2000 B.C. V. 2 covers Bronze Age to Early Middle Ages, c3000-A.D. 1000.