I am wading through an historical tome right now - it is a genuine doorstopper. Wish it was an ebook.....
One kindle benefit (there are many) is the way you can easily build your vocabulary. Just touch a word and you get the dictionary definition. It is very easy to gloss over word as we all know - we can discern the meaning, but when put on the spot some things are hard to define. So this feature is very useful.
What makes it great is that you can then bring up a list of all the words you have checked. You can then run through them quickly - if you need to check the definition again you leave them on the list. If you don't, you can remove them. This dynamic list is an awesome tool.