+1 on the iPad 3. Forget the built-in PDF reader, though. Definitely get GoodReader. It's $5 but well worth it for reference material.
Originally Posted by HarryT
The SD card slot "issue" is a total non issue, to my mind; even the smallest 16GB model has sufficient storage to store thousands of documents. Books are not large files, on the whole.
Not strictly true. My technical PDFs and manuals clock in at 80MB a piece (lots of images and diagrams) so 1,000 of those would be ~80GB. Scanned documents (300dpi, unoptimized) clock in at ~100-300MB so it'll hold even less of those. That said, 16GB is still plenty of storage and can hold a sizable amount of material.