There is no Frigate like a Book To take us Lands away
To start us off, the speaker compares a book to a frigate, or a big ship.
What to ships do? They take us places.
These lines say that a book is even better than a frigate. A book is like the best boat ever, which carries us away to far off lands.
Nor any Coursers like a Page Of prancing Poetry—
Here the speaker compares a book (in this case, a book of poetry) to a high-spirited, light-footed horse ("courser" is an old-timey word for a knight's horse). And guess what? She says that reading is even better than taking a ride on this great horse.
Line 4 refers to poetry as "prancing," which cleverly plays upon the terms commonly used to talk about poetic meter, like "metrical foot" – for more on this concept, check out the "Form and Meter" section.