Sub $250 tablet for reading textbooks?

I've been looking for something to primarily read textbook PDFs on, but I am reluctant to spend more than $250 on it. Preferably, it would have a 10"+ display and FHD or higher resolution. If possible, an aspect ratio other than 16:9 would be great, but I am willing to forgo that if I have to.

After some searching, the best I could find was just an iPad 3 on Ebay ($180), but a 9.7" display is slightly on the small side, and I don't know if it would be comfortable to read two column textbooks on a screen that small. I am also unfamiliar with the PDF reader offerings on iOS. Is there anything better?