Aren't the Harry Potter books finally available, legally, in Ebook format? As of roughly 6 months to a year ago?
As for the writting, I think JK Rowling is a fairly decent writter. Not the best I have ever read, very, very far from the worst I have ever read. Seperating the writting quality from the entertainment value the best I can, I consider the entertainment of the books extremely high. On par with some of the better books I have ever read for entertainment's sake.
I have read a number of better writters works, but most of those writter's works are not as entertaining if that makes sense.
So to me, she overall excells as a decent writers and a very entertaining author.
Within the realm of fantasy, I think J.R.R. Tolkien was a better writter, but at the sametime I don't think his works were quite as entertaining. I love the books and DO find them entertaining, but they became bogged down a little too often in explanations, histories, etc which detracted a bit from overall entertainment value.
On the one hand I'd give one a 7 for writting and a 9 for entertainment value, the other I'd give a 9 for writting and a 7 or 8 for entertainment value.
Most other highly entertaining fiction I have read tends not to be as well written or at some point becomes rather pedantic in terms of chracterizations, dimensionality of characters etc. For example, David Weber. I find his writting very entertaining on the whole, but he tends to have charaters that consistently fit in to almost exactly the same mold...which in some cases (Honorverse series) can get a little tiring after, say, more than a dozen books with basically the same sorts of characters (the villians are almost always the exact same kind of villians, the heros have almost all the same traits, etc).
HP tended to have characters who didn't simply fit in to the same mold. You have a tragic hero, reluctant hero, bumbling hero, secret hero, true evil villian, villian who finds redemption near the end, the zealot (well, several), the wiseman, etc. There were relatively few characters who fit in to the same character mold as other characters, which is part of what I liked.
Things also weren't always quite as obvious as they first appeared and the world she managed to build, at least in my mind's eye, was vivid and well fleshed out.
There were litterary mistakes, a few things glossed over or not mentioned, etc. However, on the whole it was pretty good writting, especially for such a long series to have a high level of self consitency.