they?? 그리고 의미파악이 안되네요.ㅜㅠㅜㅠ

the library of my adolescence in buenos aires contained almost every book that still matters to me today. generous teachers, passionate booksellers, friends(for whom giving a book was a supreme act of intimacy and trust,)helped me build it. their ghosts kindly haunt my shelves and the books(they gave)still carry their voices. i have the impression not of reading the book myself but of being read to. this is one of the reasons i never feel alone in my library.

여기에서 밑줄 친 they(their)은 누구를 의미하는 건가요??
그리고 그들의 영혼들이 친절하게 나의 선반을 출몰했고 그들이 주었던 책들은 그들의 목소시를 여전히 가지고 다닌다. ?? 이게 무슨의미이죠 ?? 의미파악이 잘 안되요..ㅜㅠㅜㅠ 친절한 답변 부탁드립니다.ㅜㅠ