Tablet PC's are the largest of the convenient portable readers. While laptops are usable as eBook readers they are not nearly as convenient as other devices due to the awkward keyboard arrangement and even more awkward use in portrait mode.
Tablet PC's typically have a 10 inch or larger screen and if they have a keyboard it can be folded out of the way under the unit. The fact that the keyboard remains attached is how they differ from a 2-in-1 laptop. They are also generally the most expensive, typically even higher cost than a laptop. They compete with Web Tablets, also know as Internet tablets, and some UMPCs which have smaller screens but are even more portable.
The Surface Book is the latest example. While the keyboard can be removed it is designed to be reattached so that the tablet portion can be used with the keyboard attached. A 2-in-1 requires that the keyboard be removed to use it as a pure tablet.
Tablet PC's feature a touch screen and are really overgrown PDAs with a full blown computer operating system. Typically they run Windows XP Tablet version, Windows Vista or Windows 7. There are Linux versions as well for less money. Modbook is an Apple MacOS X tablet computer. Microsoft entered the hardware business with the Surface Pro products running Windows 8. An optional keyboard turns a tablet into a 2-in-1 laptop. Other vendors are also using this OS for Tablet PC's.
A touch screen is central to the idea of a Tablet PC. These generally use a special stylus that is integral to the design. Generally they will not work with your finger or the stick type stylus used on a PDA. Most units include writing recognition software so you can just hand write on the screen and it will be corrected into typed text.
Microsoft has release a special version of the Microsoft Reader that takes advantage of the touch screen. In addition there are several other applications designed to take advantage of the screen.
Most Tablets are either Slates or Convertibles. Slates have only a touch screen although external keyboards can be used. Convertibles have a laptop look with a built-in keyboard but then the screen can be rotated and folded down or can be slid over the keyboard so that it looks like a slate, although thicker and heavier. Of course a keyboard is also available on the touch screen.
One of the big negatives to tablets is poor battery life. They also tend to be heavier than other portable solutions. Microsoft has released its own Tablet called Surface Pro 3. See 2-in-1 for similar devices that can remove the Keyboard.
 For more information
- What is a Tablet PC by Microsoft
- http://www.tuxmobil.org/tablet_unix.html - Linux versions.
- Lenovo Yoga laptop series - This is really a Tablet PC but advertised as a 2-in-1
- HP Omni 10
- Surface Book with a reversible removable keyboard.