First of all, don't worry, I won't spoil anything about this film because I'm too lazy to summarise the plot since it has been already summarised by many other reviewers.
I have read the book and watched this film twice, and here is my final review on this film: - very well abridged and modified. - very well acted by all actors, especially by Dakota Fanning. I am not British but I am quite familiar with some British accents by watching many British TV series and listening to British youtubers. And as far as I can say, Dakota's British accent seems to be quite flawless. Of course, if you're British, you are welcome to disagree with me.
The only minus point: I am still wondering if Olivia's blonde wig was necessary. Or maybe she should have dyed her hair to make it look more natural. But even if those two actors (Olivia and Dakota) had kept their natural hair colours, the film would still have worked because the script was perfectly written.