Translation:The girl not only bought the book but read it too.
While people are often sloppy and we can figure it out from context, technically the two sentences me different things in english. In 'she not only bought the book' the 'not only' is modifying the verb, so she didn't just buy the book, she did other stuff to it (read it, in this case). But in "she bought not only the book" the "not only" modifies the book, implying other things were also bought.
It's not too removed from English: но и separately would be "but" "and" - so it's not too far a leap to think of it as "but also" - which I think is a more easily grasped translation, instead of sticking "too" at the end of the sentence: но и прочитала её = "but also read it".
Yup. Loks like you shouldn't put finished on that. She read it, which kinda means she finished it, but since the phrase doesn't say finished in russian, you shouldn't use it in english.
It's one of those examples where it matters to duo not only the meaning but also the way to say it.
The use of the perfective in the past does indicate that the action was completed where the imperfective in the past means the action progressed for an unspecified or continuous time, similar to how we make the distinction: "she has read the book" and "she was reading the book." At least that's how I understand it.
Absolutely. I deliberately left out the "too" to see if they would accept it. They didn't. However, it's not necessary. I actually don't mind these slip ups too much. After a while you can kind of guess what they won't accept, and it's impossible to cover everything with any language. (Though I hope they correct it!!!) On reflection maybe that's possibly because I'm a native English speaker. These things could be confusing for others when translating into English.
Apparently купить is a strange case because it is actually perfective. The imperfective form is покупа́ть. Most often the perfective form has some prefix in front but this is one of the few exceptions.
There's an example sentence in one the lessons with покупа́ть, something like "I always buy bread (or something else) in this store": "я всегда покупаю хлеб в этом магазине".