When and how much assigned independent reading you give your 4th grader depends on your child. Some children are ready and eager for more independent reading and others need to ease into it more slowly. You want to challenge your child, but not frustrate him.
If you think your child is ready for assigned reading, then start with one book that you think your child will be able to read and comprehend. Books are read in their entirety at the pace they are scheduled, a few pages to a whole chapter per lesson. When your child finishes the first assigned book, then evaluate how he did with it. Did he struggle with the reading? Did he read and comprehend what was being read? If your child does well with one book, then you can assign two books to be read independently for lessons.
As far as assigning your child a separate formal literature book in addition to the family read aloud, many parents make good literature available for their children as free reads. There are so many good literature books available and not enough time in the scheduled school day to read them all. So, by all means, encourage your child to read some in addition to your family read aloud. However, if your child usually selects lighter books for free reads, then feel free to assign a few independent literature reads throughout the school year.
