"Navigation" is a very broad topic that includes all of the skills needed to voyage from one place to another: hydrodynamics, aerodynamics, meteorology, hydrology, position and course determination (also called "navigation" when beyond sight of land - otherwise called "pilotage"), navigation
rules of the road, engines (though purists don't have them), physical and electronic aids-to-navigation... it's a long list. Taken from its roots, the term "navigation" merely means: "to move a ship," and it is very unspecific. If you could elaborate on what specific topic you'd like to learn first, answers here may be more helpful. Otherwise, you'll need a whole library of books
For a beginner learning sails
and sailboat configurations, I have given many beginning sailors this book: "Plain Sailing: Learning
to See Like a Sailor: A Manual of Sail Trim" by Douglas Murphy.
My experience is that many people read a few books
on the theory of sailing, then go out and sail. After that, they identify areas where they need more knowledge and read more books. Then they sail some more. This pattern repeats until they feel comfortable. Taking a beginner's course may include the books you will need to start. Then it's up to your motivation and curiosity to go from there.
But learning to sail only through books is about as futile as reading only books to learn how to fly. You'll need practical experience to become proficient. You need to learn a "sailor's sense" that's in your bones and nerves. The sooner you get that experience, the more sensible will be the theory you acquire from books.