Predecessors
The Apple Newton recognised handwritten text, often inaccurately. Microsoft pushed tablets running Windows with a pen, which were heavy and expensive. It took the iPhone to show that a touch interface designed for fingers works.
E-readers
The Amazon Kindle uses electronic paper (e-ink), which does not shine into your eyes and lasts weeks on a battery charge. For reading books it is still better than a tablet.
Tablet or laptop?
A tablet is great for consuming content and for travelling. For writing and working with several windows a laptop is still more comfortable, although the line is blurring with keyboards and pens.