You're right; the options are vast! Author Eric Carle has some fabulous stories which have been transformed into toy books with gorgeous interactive elements. His famous story, 'The Very Hungry Caterpillar', is a delightful book with cute illustrations and a lovely storyline which captivates young audiences.
The ToyBook version has puzzles, games, and activities focused on the story's charming characters, like matching the different fruit eating patterns of the caterpillar! It even has some nice touch-and-feel elements for a sensory experience too.
Another classic tale is 'Brown Bear, Brown Bear, What Do You See?' by Bill Martin Jr. & Eric Carle. The book has beautiful visuals and an engaging storyline which lends itself perfectly to an interactive toy book format. It's an excellent book for encouraging children to interact with nature and the world around them. This toy book includes cute plush toys of the animal characters which brings a nice dimensional aspect to the story.
Both options are fantastic for keeping kids engaged and encouraging a love for reading!