That if you have any other books by Aho, Sethi, and Ullman, they will all become authored by Doe, Aho, Sethi, and Ullman, which is probably not what you want.  Furthermore, if you want to find all books by Sethi, you are out of luck, because "Aho, Sethi, and Ullman" doesn't match "Sethi".

This is what normalization resolves.  You need a third table with three columns: book id, author id, and author sequence number, with rows {(BOOK01, AUTH04, 1), (BOOK01, AUTH05, 2), (BOOK01, AUTH06, 3), ...]}, where AUTH04-06 are Aho, Sethi, and Ullman respectively, and AUTH01 can be removed altogether.