A few of the places you can buy the book:
Your Local Bookstore – Most local bookstores carry TGWS or can order it for you.
Amazon.com:
http://www.amazon.com/Great-Wide-Sea-M-H-Herlong/dp/0670063304
Barnes & Noble:
http://search.barnesandnoble.com/The-Great-Wide-Sea/M-H-Herlong/e/9780670063307