If you can get a good price on an older IPad you could go that way, or if you want to go the route of android there are many out there that work well as just an e-reader.
I would recommend taking a look at the transformer prime tf300. It offers quad core cpu, they advertise I think it is 12 core gpu, great battery life, stellar battery life if you get the keyboard dock/battery down the road which turns it into a netbook type device with around 14+ hours of battery life. It has 32Gb internal memory as well as an expansion slot for up to another 32Gb. Mini HDMI out to connect it to the TV if you wanted to. The tablet itself will run you $399.99, the keyboard dock $149.99. But if you are already considering an IPad2 or IPad3, 399.99 for the tf300 is a better price for a whole lot more.
If you were looking for something smaller, like a 7" the best deal out there is the Nexus 7 for $199(8Gb) and 249(16Gb). but that is only if you consider under the hood. Devices like the galaxy tab 7 have better expansion and memory options but weaker in the processing department.
Any android device will be able to access both barnes and noble as well as amazon for text books just like the IPad can.
There are cheaper options if you decide on android, but there are only 2 options if you go apple, expensive, and more expensive, comparitively speaking versus android tablets. It's really just a matter of what you want versus what you absolutely need combined with your budget.