As the name implies, the book of Exodus is focused around the Israelites’ exodus from Egypt. This is one of the most important events in the history of God’s people; many times, for the rest of the Old Testament, He will refer to Himself as “the LORD who brought you out of Egypt”.
The reason this is such an important event, and that the LORD refers to it when naming himself, going forward, is that it’s all about Him. Everything that happens, during the exodus from Egypt, happens in such a way that there is no doubt in anyone’s mind that it was done by the LORD. Then, for the latter half of the book (or thereabouts), the focus moves to how the Israelites are to live for God. He presents them with some rules to live by, and some detailed instructions on how to build the Tabernacle, where they will worship Him.
We sometimes forget, when reading the book of Exodus, that this is really God’s introduction to the Israelites—before this time, they didn’t know much about Him. Before the book of Exodus, they didn’t even have the Ten Commandments; they knew it was wrong to murder, because He’d told them that, but they really didn’t know much about God, compared with what they knew after He revealed these commandments to them. They knew that there was a God, and that He had made a promise to Abraham, but they didn’t really know a lot about His character.
They will continue to learn about God in the books to come; much of the books of Deuteronomy and Leviticus will be devoted to laws, rules, and regulations, that the Israelites are to follow.