It might seem strange to refer to conflict for non-fiction books, but I think of it more as introducing the reason for your readers to want to learn whatever it is your book has to teach them. For example, I recently discovered a YouTube video for mermaid lovers who want to swim like mermaids. The video explained what the conflict was: Buying professionally created mermaid tails is very expensive and many people can't afford them. And it presented itself, a video on how to make your own mermaid tail inexpensively, as the solution. In a travel guide, the conflict is that you want to travel but don't know which hotels are the best or which sights there are to see in the place you want to visit. The travel guide itself is the solution to the conflict.
In non-fiction books, the conflict is implied rather than written into the book. The book itself is the solution to the conflict. If you want to learn more about Christopher Columbus, you find the solution - a biography about him. If you want to grow your own garden but don't have a lot of garden space, you might find that a book about container gardening will give you the answers you need. If you want to sell your own house, you can easily find a book on the subject which will help you learn what you need to know.
Fiction novels have a deeper dependency on conflict within the story. Without conflict in a fictional story, you won't have much of a story. Conflict is the driving force in the story. The conflict that your character faces drives his or her actions. The goal of the story is for your protagonist to overcome the conflict. There can be other conflicts in the story which help to fuel the main conflict, such as your character having an argument with the one person who holds the answer to something your protagonist needs to know or your protagonist and his or her charming secondary character/sidekick getting separated and needing to find each other again before they can, together, defeat, whatever it is that's causing the original problem.
If done correctly, the journey to overcome the conflict your protagonist faces, should, in some way, change your protagonist. He or she should grow as a result of defeating the obstacles along the way. Every decision your protagonist makes and every event that occurs as a result of those decisions should help shape your protagonists later decisions.
There are four main types of conflict in stories: man verses man - you have a protagonist and an antagonist pitted against each other, man verses self - where the biggest challenge for the protagonist is to overcome his or her own shortcomings, man verses nature - where man must overcome the forces of nature or creatures within nature to survive, and man verses society - where man must overcome the restrictions of society in order to succeed. These can sometimes overlap in stories. Others have suggested that there are more types of conflict for modern stories, such as man verses fate, man verses the supernatural and man verses technology, but, again, many of these types of conflict will overlap within stories.
If you are writing a non-fiction book, ask yourself; what is the implied conflict for which my book is the solution?
If you are writing a fiction novel, ask yourself these questions:
What does my protagonist want?
What obstacles or problems is my protagonist facing?
How will my protagonist need to change, or what will he or she need to do differently, in order to overcome the obstacles or problems being faced?