"Think of a book like a really big door, preferably one of those Parisian ones that are thick and heavy and last hundreds of years. Here's how it breaks down.
The premise is what happens to knock the door ajar. Something sets the protagonist's life out of balance. Preferably something really intriguing or like totally deep man.
The climax is when the door closes. Maybe the protagonist made it through the door, maybe they didn't make it through the door but learned a really great lesson about door closing, maybe the door chopped them in half.
The theme is how the person opening the door changes along the way. What's the plot? The plot is what keeps the door open!! Why can't that person close the door? So basically, plot is a premise plus a major complication that tests the protagonist. It's what opens the door plus what's keeping the door from being closed."
To keep a reader interested a non-fiction book should follow a similar pattern. A travel book is probably the easiest example - why did the author go, what kept them travelling, what caused then to come back, what did they learn along the way.