some or about

He borrowed about five books from me.

"Some" is incorrect.

Thank you dear AlpheccaStare,
Sincerely, I saw an example that I didn't know which one is correct, and one of the meanings of "some" is approximately. Would you please explain that to me?

Cambridge Advanced Learners Dictionary's example: "The water is some twenty to thirty meters beneath the ground."
thefreedictionary.com :Approximately; about: eg "Some 40 people attended the ral

Hello Paeez, I think that both are correct, but we would use "about five books" more frequently than "some five books". The Shorter Oxford Dictionary says "Some (with following numeral adjective) is an approximate amount". That is my understanding of it - to give a general estimate.

Yes, in some situations, "some" can mean approximately.
But it is rather rare, and used in situations where you know the broad picture, but you don't have enough detail to count individuals or measure.
In a crowd, you can guess (but not count) the number, and the water table depth can vary in that general area between two distances.

"five books" it is just too specific to

Thank you kindly, AlpheccaStars and Moincent,

I guess I understand your points, and I usually use "about" before nouns to embed the meaning of approximate in a quantity. However, I didn't understand if there is some certain situations that I should preferably use "some" instead of "about". When I read "some" in such situations I feel ,somehow, that the speaker has a quite good estimation

Paeez I didn't understand if there is some certain situations that I should preferably use "some" instead of "about".

You can always use "about."
As I remarked, the use of "some" is rare.

Thank you.