If your child is having difficulty with reading, and you can afford it, get a Kindle, or other e-reader.
Not only will your child become more engaged and motivated with their new gadget, but with the Kindle you can make the font bigger and spacing between lines wider. This change makes complicated text (usually with a smaller font) look more like a beginning chapter book. By changing the size of the font, it is easier for the reader to track the words, aiding with reading fluency. (There is a reason those easy readers have a large font and fewer words on the page.)
Looking up vocabulary words is also instantaneously accomplished with a couple clicks. If you want to see something laborious, ask a profoundly dyslexic student to find a word in a dictionary! A deep vocabulary is one of the keys to reading comprehension. Because of the ease, barriers are lifted and the child is no longer guessing about unknown words.
And it doesn’t hurt to be able to buy a book instantly.