If you're looking for a vintage slate Tablet, the best one ever made IMHO was NEC's Versa T400. Especially for reading ebooks
I had it for about a year, then sold it because i needed the money (for other gadgets
). It weighed 1kg (2.2lb), was thick 1.5cm and had almost exact footprint of an A4 page. You could easily hold it in one hand for long periods of time and it never heated up above lukewarm levels. It used a Wacom digitizer (with a non-powered, or, actually, inductive pen) with pressure sensitivity and came with two pens - one stylus sized, without pressure sensitivity and an eraser, that fit inside the tablet, and a larger, typical Wacom pen, with all the bells and whistles. It was
ideal for reading, quick jotting on the go and quick/light graphics editing.
It's only downsides were relatively non-impressive battery life (around 2.5-3 hours of averagely to slightly above averagely intense use - read: light Photoshopping) and limited storage space (20 GB HDD, and it was very hard to replace it, because it was of the slim, 5mm kind).
I kinda regret i sold it... :/