I have a 10.1 inch tablet and use it to read books. Reading most RPG books is a challenge, since many of them are laid out in 2 column format, with a lot of art, and with relatively small print. So you end up having to pan around a fair bit. But logistically it's hard to beat the ability to carry around 300 rulebooks and supplements on one lightweight device.
In general I find it workable for either straight read/skim-throughs of new books, where you're not jumping around a lot, or for quick reference to bits and pieces, depending on how well the publisher has done their indexing. It's not great for really "using" a book, like when you're making a character in a complex system and need to do a ton of jumping around between sections. Paper (and copious bookmarks) still works best for that.