Lepore did write a book: https://www.goodreads.com/book/show/27071492-joe-gould-s-teeth?ac=1&from_search=true
I haven't read the book, but I read the original article that she wrote for The New Yorker, and there wasn't much to that. From most of the reviews, it doesn't seem that there was much to what she came up with. Joseph Mitchell seems to have gotten it right in his mid 60's New Yorker articles and later book.