This book is called "The Second Book of the Faerie Queene contayning The Legend of Sir Guyon, or Of Temperance." Say that five times fast.
Addressing Queen Elizabeth I, again (get used to it), the narrator worries that people will accuse him of inventing all his stories about Faerie Land.
But, people are discovering new worlds all the time, like Peru and America, that were hidden from human knowledge for centuries before, so who can say for certain Faerie Land doesn't exist?
Brain bite! When Spenser is writing The Faerie Queene in the 1590s, Europe and England are at the height of New World discovery and colonization. So when Spenser talks about new worlds, he's being pretty literal since places no one has imagined existed were being discovered regularly.
Even though Faerie Land is far away and yet to be discovered, the narrator also urges the queen to think about it as a reflection on herself and her kingdom. And with that begins the story of Sir Guyon.