Your book has four months to fly off the shelves.
If your book doesn’t sell in the first four months of its bookstore life, it will be remaindered and disappears from bookstores und could end up at “A Buck a Book”. 90 to 95% of books don’t pay back their advance. Royalty will only be paid if the advance is paid back. What you get up front as an advance is usually all you will ever get.
If you screw up on your first book, you’re out.
If you do well with it, publishers will be eager to see your next title. But if you don’t sell a lot of books, your publisher might not be returning your emails and phone calls when it comes time to offer your second book.
Sorry, no publicity.
Ten years ago, publishers did some marketing for books. Now they might send out some galleys and wait to see if anyone is interested. Then they focus all their publicity on the books they expext to be a bestseller. If you want your book to be a success, YOU will have to do all the publicity yourself!
Traditional publishing is very slow.
Unless you’ve got a political tell-all, your book is going to ”be in the making” for two years or longer until it goes into the bookstores. You need to be sure your topic is timeless und that you will be interested in publicizing it three years from now.
Most likely your book will not be published in foreign countries.
Unless you have a savvy agent (preferably speaking several languages) who is trying to sell your book abroad, there is little chance that your publisher actively tries to find buyers in foreign markets.
On the top
If you are interested in making money or selling your book for a long time, better consider e-books and self-publishing.
But in any way, marketing skills or at least the willingness to learn about marketing and PR to promote your book, are essential for an author.
Books don’t sell themselves, as most writers sooner or later find out – often too late.