...，在摊里看，每册1分钱，选好书坐下就看，看完连书带钱交给摊主；假如借走回家看，则每本每天2分钱，挑好书后交给摊主，...
This is from the Standard Course Book of HSK5, segment 20. What is the meaning of 走 in 假如借走回家看? Actually, it looks like it means to go, but it doesn't make sense to me, since the sentence makes the same sense without it: 假如借回家看. So what is its need?
借 is the verb and 走 is a result complement, similar to 到 in 听到
Without 走 and writing 借回家看(borrow it back home to read) doesn't change the meaning of the sentence
with 走 in 借走回家看 (borrow it away back home to read) the sentence describes the scene with a more detailed description of the action. The reader is now told the subject borrows and takes the book away home to read, which is kind of redundant in this context because we can all presume after you borrow something, you will take it away from the lender
In another context, 走 may be necessary when there's a possibility that you borrow and use something on the spot, in that case, the result complement would be 用, as in 借用 = borrow (and use), borrow
借來 = borrow (and take in) describes how something came into your possession
What is the function of 走 in 假如借走回家看?
In Chinese, very often there is an adverb following a verb, which can be treated as a compound verb. For example,
(1) 那件大衣被别人拿走了. = Someone else took away that coat.
(2) 这本书不能从图书馆借出去. = You cannot take this book out of the library.
(3) 那个老房子已经被拆掉了. = The old house has been demolished.
You can understand the combinations just as the English phrases, such as "put on", "turn off", or "give up".
Sometimes, you can omit the adverb, but sometimes you cannot. For example,
(把书)借走回家看. = (把书)借回家看. = You borrow the book and take it home to read.
他们把房子拆掉了. = 他们把房子拆了. = They took down the house.
我们爬上了那座山. = We summited that mountain.
我们爬了那座山. = We climbed that mountain. (not necessary to the peak).
