Kids learn to read books on subjects that interest them
Teach your child to read books with pictures they like
Teach your child to browse books by looking at the cover art. As kids learn to read, even a reluctant reader will usually look at pictures without much of a struggle. Play up this habit by teaching your child that they can learn about the topic of the book by what's shown on the cover.
Kids learning to read can be hooked on stories from movies
Model for your child that after a picture grabs their attention, the next step is to read the title and author. Help children learn that the title can give a hint about what the book is about, or it might sound familiar. To make this more concrete, find a book that's currently being made into a movie that they have seen, or that they've seen commercials for on TV. Often as kids learn to read if they know there's a movie version, or has seen the movie already, they are less intimidated about reading it than a whole book with no background knowledge about what's going to happen in it.
Teach your child to read books that are an appropriate length
Help children learn that they need to check the length of books. If the book looks and feels thinner or fatter than they are used to reading, this is an indication that the book is too easy or too hard. Depending on the child's age and reading level, they can forget what happens in a book that is too long for them.
Kids learning to read need to be shown the summaries
Model reading the back of the book aloud to your child. Not every book has a synopsis on the back cover, but those that do help children learn if the book is really what they were hoping for when they saw the cover art and they picked it out.
Help children learn the 5 finger rule to gain independence
Help children learn the "5 finger rule" test to see if the book is too easy or hard. First have the child open to a page in the middle of the book. Have them read one entire page, counting on their fingers how many mistakes or times they get stuck on a word. If they make 2 or 3 mistakes this book is likely at the appropriate reading level for him or her. Teach your child to read books that fall into this category. Any less and it may be too easy; any more and it may be too hard.
Provide encouragement. Not all kids like to read, and not all children learn to read at the same pace. Let your child know you're proud of him or her when they do choose a book to read, even if it's not the quality literature you may be hoping for. They'll get there. Good luck!
If giving your child free reign in the bookstore is too overwhelming, limit his or her choices. Select a pile of books that you think are topics he or she is interested in. Having some variation in the length and difficulty is a good learning experience in helping your child choose what's appropriate.