West Asia has been the home of many of the world’s most popular religions, and has always been a hotbed of new religious ideas. Religions may have gotten started in West Asia because empires got started there. Some historians think that centralized, organized religions form as a kind of response to centralized, organized empires.
There are some ideas which have lasted over many thousands of years, and others which come and go. There seems always to have been a tendency in West Asia towards monotheism, the belief in only one god, or the belief that one god is much more important than the others. But at other times, people have believed in many gods (polytheism).
Another West Asian idea is that of the holy man or holy woman. This is the idea that some people are somehow closer to the gods, or to God, than other people are. These holy people may hear God speaking to them, or they may just be wiser and more helpful than other people are. Special signs, like their bare feet, or their ability to do miracles, will let you know who they are.
There has also been a long interest in the idea of sacrifice. Some people have sacrificed animals, others (like the Phoenicians) have sacrificed their own children. Zoroastrians were known for their fire sacrifices. Christians believed that it was no longer necessary to sacrifice, because Jesus had already sacrificed himself. The Jews kept on sacrificing until the Romans destroyed their Temple.
Because of the mixture of cultures in West Asia, there has also been a lot of interest in how my gods might get along with your gods, or what happens when two groups of people worship different gods. Indeed, the whole history of West Asia might be seen as a series of conflicts among the gods, played out on a human stage.
Ancient Mesopotamians, by Elena Gambino (2000). For kids, retellings of Mesopotamian stories and lots of context.
Gods, Goddesses, and Monsters: An Encyclopedia of World Mythology, by Sheila Keenan (2000). Easy reading.
Religion in Ancient Mesopotamia, by Jean Bottero (2001).
God Against the Gods: The History of the War Between Monotheism and Polytheism, by Jonathan Kirsch (2004). From Akhenaten in Egypt, through Judaism and the rise of Christianity. Lively, popular writing.
A World Full of Gods: The Strange Triumph of Christianity, by Keith Hopkins (2001). Entertaining account of what it was really like at non-Christian and early Christian religious events. Not for young kids.