In addition to the themes other educators have provided, these are two others which emerge in the Old Testament book of Exodus.

God can be depended on

When Moses was born, Pharoah had issued a decree that all male babies should be killed. His mother, in faith, placed her new baby in a basket and placed the basket by the river bank. God sent Pharoah's own daughter to discover the infant, and she took him home, sparing his life. Moses's sister witnessed the rescue and offered to find a Hebrew woman to nurse the child. God provided a way for Moses's biological mother to spend time with her baby and spared his life; he grew to be a great leader for his people.

Later, when Moses led the Israelites through the desert, they complained that they would have rather died at the hands of Pharoah than suffered the hunger they were experiencing in the desert. God promised Moses that he would send bread raining down from Heaven to feed them, and he was faithful to his promise. God's only requirement was that the people not store any for the next day, proving that they believed that God would continue to provide for them each day. Throughout the book of Exodus, God proves that he is faithful to his promises and can be depended on.

God desires a relationship with His people

When the Israelites were in the desert, God wondered why they complained against a sovereign God who always provided for them. In order to exist in a harmonious relationship with God, He provided ten commandments for His people to follow. God desires honor as the ultimate creator, yet he also desires fellowship with his creation. God established rules for people to follow to live harmoniously with each other and therefore in harmony with their Creator. In chapter 33, when God asked Moses to leave for the land of milk and honey, Moses asked for God's assistance:

Then Moses said to him, “If your Presence does not go with us, do not send us up from here. How will anyone know that you are pleased with me and with your people unless you go with us? What else will distinguish me and your people from all the other people on the face of the earth?”

And the Lord said to Moses, “I will do the very thing you have asked, because I am pleased with you and I know you by name.”

Moses and God shared an intimate and personal relationship, and this is a model of the relationship believers should still seek.

Knowing and Making Known

God expresses the desire to know Israel and for the people of Israel to know him. In Exodus 3:15, God, addressing Moses, tells him that he, God, is to be remembered throughout all generations. God instructs Moses to tell the people of Israel that he, Moses, has been sent to them by the Lord, the God of Abraham, Isaac, and Jacob.

As Exodus progresses, God gradually reveals himself. We see God as the God who remembers, rules, rescues, judges, speaks, provides for, and dwells among his people. God remains a transcendent figure to whom all glory and honor are owed. But he also shows the immanent nature of his awesome divinity as he comes to dwell among this chosen people.

The Covenantal Relationship between God and the People of Israel

Exodus develops the covenant first handed down by God to Abraham in the Book of Genesis. The Mosaic covenant established with the people of Israel at Mount Sinai carries forward the purpose of the original covenant. In Genesis 12:1-3 God had promised that he would make Israel into a great nation, and the Mosaic covenant of Exodus represents the next stage of fulfillment of that original promise.

1. God is sovereign and Almighty.

2. Man cannot uphold the Law, but is in need of a Savior.

If we were to synthesize the myriad of topics found in the book of Exodus, we could conclude that the two most important messages that we get out of the book are the following:

The Israelites are the chosen people of God:

The God of the Israelites is the god of Moses, as well as the god of Abraham. His name is "I AM" (or "I AM who I AM", also, Yahwe, Jehova, et al), and he declares himself as the liberator and protector of his people. To the modern reader this may sound obvious, but we are talking about a writing created during a time when these tenets were imperative to the Israelites as confirmation of themselves as a nation.

Coming straight from slavery into the possibility of a new land, the people of Israel needed several forms of validation to begin their journey. Having the validation of God means that they could move forward as an independent nation. The final confirmation of God's commitment to the people of Israel is sealed with the final covenant between themselves and God, found in Exodus 20 - 23 and 25:12.  From that moment on, Israel would be God's covenant-nation, ruled by the holy principles found in the Commandments. 

The second most important theme found in Exodus could clearly be:

God is Almighty.

Exodus illustrates in several occasions how the God of the Israelites "I AM" is quite almighty. It is in this book where we see their God manifest most furiously in the most dedicated fashion. First, God assists in the liberation of the Israelites from Egypt by giving 10 divine plagues to the Egyptians. This is proof of the wrath and power of a God that demands that his people are freed. These plagues were, in order a) the turning of water into blood,  b) infestation of frogs,  c) gnats, d) swarms of flies, e) death to the livestock  f) boils, or bubos, on the skin of the Egyptians, g) hail,  h) locusts,  i) darkness, and the worst of all: the death of every firstborn in Egypt (7:19-11:5)

Also, God does the well-known parting of the Red Sea to allow the passage of the people. Moreover, He also provides for the people light and guidance throughout their journey. 

The Lord was going before them in a pillar of cloud by day to lead them on the way, and in a pillar of fire by night to give them light, that they might travel by day and by night. He did not take away the pillar of cloud by day, nor the pillar of fire by night, from before the people (Exodus 13:21-22).

He also provides them manna for their survival in the desert (16:35), and protects them even in times of weakness from the part of the people. 

In all, God's confirmation of his purpose with the people of Israel, as well as the clear proof that He is an Almighty God, are the two most important themes that come out of the many events that take place in the book of Exodus.