1. We have many good books.

2. We have many great books.
[Great means 'very good'. What difference do you have between 'good' and 'great'? When we think of the title of a book, "Good To Great," they have different meaning. Is that right?]

3. I have a good many books.
4. I have a great many books.
[They seem to be the same in meaning, don't they? Do you have any difference in meaning because of the words, 'good and great'?

1 answer

The difference between "good" and "great" in 1 and 2 is only in the enthusiasm of the speaker or writer! A person who thinks something (a book, a movie, or ??) is REALLY good, he or she might say or use the adjective "great" but that's about it.

In 3 and 4, there's really no difference.