The first sentence is correct. The second, while not incorrect, sounds a little awkward. The reason is because your object is a complex one, with modifiers (rather than saying a "novel," you said "a very interesting novel.) So where should you place the object of a sentence if a directional verb complement is used? A simple object, such as a noun without a number word and measure word; a noun without a descriptive clause; and in particular an object which is a place word e.g., 家, 学院... should be placed in the middle of a combined complement. For example: 她走进房间来 She walked into the room. (The speaker is in the room.) Normally a complex object such as a noun with a number, measure word or a descriptive clause can be placed after the combined complement 去 or 来 . 她拿出来了一张非常漂亮的画

Both correct, but they have different meanings. The first one means she has borrowed a novel from library. The second one means she is on the way to library to borrow the book or she is in the library and borrowing the novel. And the speaker of the first sentence is out of library, maybe live with Lanlan. The speaker of the latter one is in the library.

Both are correct, but the first sentence is more nature

in the 1st sentence 借来了 is one word

Hmm,I think the main problem is this "来"(prep.)(sometimes it equals ''to" in English)。Usually,we put this word behind a verb. For example,we are going now.(but if we wanna to express ourselves clearly),we can add a 'to' behind 'going',(we are going to the park now). 兰兰从图书馆借来了一本很有意思的小说。兰兰从图书馆借一本很有意思的小说。the only difference between these two sentences is the tense. The former one,is past tense,and the later is present tense.