[LoneTech]

You won't fry your reader with a USB type DC supply. USB uses constant voltage (5.0-5.5V), and devices that use more than 100mA current are required to manage themselves (normally 500mA is max). That 200mA rating on your charger is probably for the DC output, and would mean the PocketBook isn't very power hungry (typical cheap chargers tend to be 300mA, too little for a PSP).

The real problem tends to be the crude workarounds employed to detect dumb chargers. When plugged into a computer, devices may not draw over 100mA until negotiated - and the chargers don't have that negotiation function, so a few brands use various non-standard simple circuits to mark their chargers. If the device and charger are designed using differing tricks, you may get slow or no charging.

I don't expect any problem using that phone charger, but there's a risk it'll only charge slowly. Luckily ebook readers have fairly low demands.

P.S: Those wireless chargers may represent a significantly higher risk. They normally use air transformers, i.e. induction, and that will do the same to your circuits as an induction stove does to your food. The question is to what degree.