It’s the beginning and more specifically the first sentence, then paragraph, then page, then chapter. You have to grab your reader the minute they pick up your novel.
When you are ready to submit your work to an agent, one thing you will notice is they don’t want your complete work. They only want the first few pages, or some may ask for a couple of chapters. Don’t be bold and overconfident sending them the entire thing.
They probably will toss it to the side for your failure to follow instructions. If they do read, they won’t get very far if the first few pages aren’t compelling enough to draw them in (which was the part they wanted to see in the first place).
Agents as a rule, don’t want to see the entire manuscript until they know you can write a compelling story. You have to make them want to see more. Leave them hanging on the edge of their seat. They will ask for the rest of your manuscript just to find out what happens next.
That’s the same thing that will happen for your readers. You want to do an e-book and bypass the literary agent, that’s fine too, but your readers will do the same thing the agent does. They will read a sample prior to buying the book. It had better be compelling from the beginning or you lost a sale. Remember you’re asking people to invest time and money when they purchase your work. Make it worthy of their interest.
Look at your first chapter as a promise to your readers. Remember your first pages set the tone and ground rules for how you will tell your story. No matter how polished your manuscript is, how compelling your characters are, how tightly you’ve plotted the story, that first chapter has to draw the reader in or they will never know.