You can start reading potty training books when your child is around 18-24 months old. These books are designed to introduce and familiarize your child with the concept of using the potty. Reading potty training books together can help spark interest in the process and make it a fun and engaging experience. Look for books that are age-appropriate and have simple language and colorful illustrations. Some popular potty training books include "Potty" by Leslie Patricelli, "Once Upon a Potty" by Alona Frankel, and "P is for Potty!" from Sesame Street. Reading these books can help your child understand and get excited about potty training. Remember, every child is different, so it's important to gauge your child's readiness and interest before introducing potty training books.