A book is made of many sheets of paper or parchment, bound together down one side. Each sheet is called a leaf, and each side of a leaf is called a page. Books can have lots of pictures or just words. They might have a story in them that is all true (non-fiction) or a story that someone has made up (fiction). Reading books is a hobby a lot of people enjoy.
A brook is a very small, running stream of fresh water. Brooks often come from a spring.
A cook is someone who prepares and cooks food for a living. A cook in a higher class restaurant is usually called a chef. Cooking is also the process of preparing food to eat by using heat, for example you need to cook potatoes before you can eat them.
A hook is a curved shape you attach something else to. Hooks are shaped so you can hang something on a hook and it won't slip off, or you hook something to something else and they don't come apart. Hooks are often used on a crane to lift things. Many birds have a hook-shaped beak.
A matchbook is a different way to store matches than the more common matchbox. Matchbooks are essentially a folded over piece of cardboard with a rough strip on the outside for striking the matches on. The matches in the matchbook are all attached together in a row, and also attached to the inside of the matchbook. They are also made from cardboard, and must be torn off before they can be used.