2.2, hands down. For just reading e-books, however, it's not worth the premium. Heck, to be honest, 1.5 or 1.6 would work fine if you could get the app you wanted installed.
7 Inch Color Ebook Reader support Various Book Format, 720P Video - US$135.00 : Euogo.com
New 7 Inch Google Android Tablet Notebook with Camera, WIFI, External USB, Support Internet Cable, IWEB - US$98.80 : Euogo.com
7 inch Google Android 1.6 Tablet PC UMPC MID Notebook with WIFI - US$92.15 : Euogo.com
Android Tablet-Various Android Talbet PC, 2.X Android Pad Check on the kickstands and keyboards in this link.
Maylong M-150 universal android tablet This is a discussion of the Maylong M-150 available at Walgreens for approximately $100
And there are TONS of other tablets kicking around.