Q&A for How to Write an Introduction to a Book

Either or both. You get to decide what constitutes "your intro" and where it should appear.

There is no established relationship between the length of a book and the length of its introduction. Write whatever introduction you feel is appropriate, and don't worry about the length.

Your introduction should not be too much longer than the average chapter length of your book.

Mail a copy of your manuscript to a publisher. If they think they can sell your book, then they will offer you an agreement, whether that be them buying the book rights from you or paying you royalties.