Visit a nearby library and get some books on a variety of topics. In order to begin, it is advised that you should select books with a number of illustrations, even if your child is a 4th or 5th grader. You're competing with television, video games, and movies so bring home material that is visually stimulating.
Explain that sometimes it takes a while for a person's attention span or reading level to catch up to the types of books that will be worth the time it takes to read. Tell your child that there is one book out there that makes each person a reader and it's not the same book for every reader. Challenge your child to find his/her book.
If you are a book reader, you will only want to read the genre you like. There is no way someone can force you to read poetry when you are a mystery geek. It's the same for your kid. If they read a chapter and it's still not a book they enjoy, try another.
Sometime just reading with your child is enough. You can read aloud or sit in the same room and read at the same time. It doesn't have to be for hours; it can be for fifteen minutes. Show your kid you value the written word and your kid will be curious to see what's up.
You can entice the kids to read more by introducing a reward system. Ask them to read the book thoroughly and then have a detailed discussion. Ask them questions and reward them for every right answer.