The Reading Rainbow of today is different than the one I remember from childhood. In the television version, a soothing voice read books to viewers as illustrations drifted across the screen like fish in an aquarium. LeVar and the gang would go on trips related to the featured books: they’d ride hot air balloons, bury time capsules, and learn sign language from Koko the gorilla. The television series also featured real-life kids trumpeting their favorite books. The Reading Rainbow tablet app is busier. It includes e-books, videos, and games, organized into sections with titles like “Action Adventures & Magical Tales” or “Animal Kingdom.” A lot of the old elements remain — field trips, books read out loud — but while the TV show was all about using the screen to get kids away from the screen, the Reading Rainbow app is about doing everything, including reading, on the screen. Will the app actually do more to improve children’s mastery of reading than any of the hundreds of other reading apps out there?