Computer Engineering for Babies is a board book with two buttons and an LED that teaches you about computer logic gates, including NOT, OR, AND, XOR and a Latch. It was successfully funded on Kickstarter and is now available for pre-order for $33.
The book has 6 pages. Each page has a different function; WIRE, NOT, OR, AND, XOR and LATCH. Sensors in the book detect which page you are on so that the buttons can have different functions depending on the active page. So when you open to the AND page, the LED is only lit when both buttons are pressed. And when you are open to the NOT page the LED is on as long as the button is NOT being pressed. And each page lights the LED with a different color.
I wanted this book to be super user friendly. Some might think it's a stupid detail, but I spent months just finding the right arcade style button with the perfect click when pressed. For a time, I was even considering injection molding my own custom buttons just to make sure I got it right. But I eventually found a button that's low profile to fit, easy to press, and has great tactical feel.
The book is also super low power, and should last about a year on the shelf. It also has a replaceable battery, so after your kid is done with it, you can just have another to get more value out of the book!