No. In fact, I'd say hardly ever.

We have books that are thousands of years old. Without explicitly copying and translating formats, media, etc., I wouldn't count on any digital format to survive more than a century - and probably be undecipherable at the end of it anyway. Some scholars have suggested that we're in the midst of what will be a digital dark age because of this very reason.

Let's also consider the sort of degradation that can creep in. I've got a 110 year old document I'm deciphering at the moment, and there are parts of letters where the ink has faded or the paper has torn. I can usually make out from the remaining bits what the letter should be. You've probably done this on old letters: "Is that an 'a' or an 'o'? On the other hand, if I have a lower-case f in UTF-32, its binary representation is "00000000000000000000000001100110." If I have minor data corruption, one or more of those bits will flip (1-->0 or 0-->1). Since it could be anywhere in the sequence, I could end up with something totally unrelated to an 'f' either in character shape or alphabetic proximity.

Then there's the reading, indexing, and searching abilities in a physical book - no "add a bookmark" feature compares to sticking a finger on the page you want to flip back to, or comparing a few pages side-by-side. Physical bookmarks, stickies, or earmarking (noooo!) are all ways that people reference books which don't translate well.

Visually, lit displays are harder on our eyes than paper books in good ambient light.

e-books of course have some advantages, especially for technical material. Being able to hit "ctrl-f" and search for a single word or phrase is incredibly valuable. Constant updates of product documentation means not having to throw away books whenever a new version of the item/software is released. Linking to references (e.g. dictionary lookup) is much more convenient than going to get another book out.

But for just sitting down and reading, the tactile experience of a real book rules over everything else in my opinion. Sitting in a coffee shop with a book in hand is a profoundly human experience. Walking through the endless aisles of books at a library is both inspiring and humbling.

So in short, yeah - there is HUGE doubt that e-books are superior.