What is better ..?

Depends how good the new ones are!

3 new books

Well having done both,after finishing one I do all I can to forget about it until I remember again so I read 3,4,5,however many more before going back to it again and remembering how good it was.

They both have their benefits, depends whether you value depth of knowledge or breadth of knowledge more.

Three new books. I never re-read books, unless I forget I've read them.

It has to be reading the new books, you know the plot of the other

Depends... Some books are worth one reading ;)

Good book, three times - at least!

Good book three times

3 new books...

3 new books