The current Enso Zenpad has a pretty small screen -- the entire device is only 5" long. Personally, I'd hold out for a 7" model if e-books is a prime, but not exclusive, requirement. I'm quite excited about what appears to be coming down the pipe for Android devices -- it looks like a veritable deluge of devices arriving in the next 90 to 180 days and from start-ups to mainstream vendors.
Nonetheless, the specs for the Enso Zenpad are impressive:
http://www.enso-now.com/specifications/
They claim forward compatibility with Android 2.x (ships with 1.6); wifi built in; 8GB SDHC card included; can expand to 32 GB. Two drawbacks: there is no HDMI output and any device which needs a stylus gives me great pause. That's also another reason to consider a larger screen. The six hr battery life is ok but the next gen are all going to be in the 10 hr range -- Apple having set this new standard. Oh yah, and there is no accelerometer -- which is pretty much a must have in this class of device.
I do like the price: under $200 which includes worldwide shipping.
As an alternative if money is really burning a hole in your pocket, there is the SmartQ V7 at under $300 including shipping. I'd also keep my eye on the Huawei Smakit 7; there are a couple of details videos online that are mighty tasty.