Once a child's intervention reading level has been determined, books of the appropriate level need to be located for that child to read in the presence of a skilled reader. However, book levelling is FAR from a "precise science."
Some guidelines for determining appropriate reading material below mid-first grade are provided here.
The UURC is currently providing excerpts from our teacher binders that give lists of leveled
Parents looking for additional books on their child's instructional level are encouraged to use AR (Accelerated Reader) lists of books. The following link lists sites that have such AR lists:
The AR lists assign books a grade and a month (i.e., 3.4 is the fourth month of the third grade), but because levelling is not precise some experimentation may be required on the parent's part. A good rule of thumb is that a child should not be making more than 1-2 errors in every 10 words as they read with assistance.
When looking for books in the library you may also find other leveling systems in place. Here is list of approximate correspondences across various systems.