In order to download free, you do need to subscribe your email address. They don't flood you with other marketing emails. You do have to act lightning fast when you get the email because these stay available free almost no time. This one is short at 128 pages.
There's a bookclub on booklikes for these at http://booklikes.com/book-clubs/88/tor-monthly-free-ebook-science-fiction-and-fantasy (TOR publishes mainly science fiction and fantasy genre books). Publisher page for book.