I long ago ran out of bookshelf space, it became so overwhelming in our living room area that they were banished to the basement and the bedroom. No space left in either of those locations either (well unless I chose to get rid of all the other things we commonly keep in those areas) and thus I purchased a Sony e-reader about 5 years ago if memory serves. I loved it and really was not looking for anything else and then along came tablets. I really had no great use for a tablet although eventually found it could replace my laptop for some off site work I occasionally do and so I dove in and got a tablet. I love it. When I chose to look something up while reading I simply call up the internet without ever leaving the book and do my search, close the internet and I am right back in my book. I have the Kindle app, B&N, Kobo, Sony, Aldiko and a few others. When I am in the market for a book and Kobo is offering me 20% off I buy there, when B&N has the better price I buy there, etc. I always check Baen books first as almost everything is $6.00 there but obviously they do not have everything so I tend to shop around and now I always check the library first.
I do find maps and other graphics to sometimes be problematic and am thankful that I can move from portrait to landscape mode which sometimes helps me to see the graphic in a more satisfying way. I do think the publishers are missing the boat in not taking more advantage of this medium and doing things like making the maps interactive with your reading so when you are at a given place in the book you can look at the map and and see the path you have followed and where you are located at now, in fact the map should pop up whenever you need or want it. When I am reading a large epic with hundreds of characters I would love to be able to highlight a name and get a short bio to remind me of who the character is and I am sure there are other things of this nature that could be done. I assume some of this will be in the future. I can even imagine a mix of mediums with short animations or film clips available to the reader (wouldn't you like to see a wonderful artists rendition of a dragon flapping through the sky or a nifty view of a new solar system or........)
Anyway I think most of those things will require more processing power than a dedicated reader and I think you can see with the new color Kindle that the future on this is just opening up. I can envision multiple e-book versions, i.e., the bare bones version for the dedicated reader at the bottom of the price scale, a moderately interactive version for a bit more and something scaled up even more with the aforementioned film clips and animations and hopefully a host of things I have not even thought of. None of us can say for sure what is coming down the road but I intend to embrace it as fully as my pocketbook allows. Incidentally the tablet I bought has the Pixel Qi screen which is very readable in full sunlight with no backlight needed and yet with a very light amount of backlighting very usable indoors and I really appreciate that since nothing beats enjoying a nice summer day sitting on the deck and reading a good book except maybe curling up all cozy in my chair with a good book when the winds of winter are blowing.