Never read it.
Saw half the swedish version and was not impressed.
Saw the new version and was excellent.
It's just so well made. The characters and the story (as they are in the others I'm sure) are really interesting. I liked it a lot.
On the subject of accents - they kind of had to do the speaking english in with swedish accents. Unless they cast Swedish actors, which wouldn't have got the green-light, then it would always be a bit fake. The only other alternative is to do it with the actors' own accents. That just wouldn't work at all. It's an unfortunate thing, but I think it was easy to get over it.
Anyway - I really don't like the backlash against the new movie - saying the original is way better. The amount of times I've heard that from people I know... I find it to be disingenuous and pretentious, tbh. The original is pretty poorly made imo, and the new one is great. I don't see the problem with remaking something to be better, if the original isn't very good.
If the original is awesome, like Let the Right One In, then a remake is somewhat unnecessary. (I havent seen the remake) But I'd still be open to the possibility of it being an improvement. I never understood the aversion to remakes.