When you are thinking of publishing your own book, there are several options. Many people read the advertisements in a writing magazine, and without researching options simply go to one of these: a company that they pay in order to publish their book. Quality of services ranges from excellent to steal-you-blind; Mark Levine has written a helpful book comparing 45 companies
The publisher becomes important when considering the ISBN. The ISBN, also known as the International Standard Book Number, is like a book's social security number: it is a unique identifier that is forever linked to your book. The ISBN is necessary to engage in generalized commerce in bookstores, online, and other venues -- in other words, you can sell a book by hand without an ISBN, say cookbooks at a community function, but that's it.
Pick up any book on your shelf. On the back cover you should see a white box with two bar codes, and also several strings of numbers. The larger barcode on the left encodes the book's ISBN, a 13-digit number beginning with *978* if it's published in the USA. Since the system recently switched to 13 digits, each book also has a 10-digit ISBN although it may not be printed on the book. The smaller barcode on the right encodes the book's price in a five digit number. The number is *90000* indicates no price specified.
Since the ISBN identifies the publisher, unless you have bought the ISBN from RR Bowker (if you publish in the USA), the book is not considered *yours.* I want to quote this section from the United States ISBN Agency, the official source for ISBNs in the USA:
Who can assign ISBNs to a publisher?
There are over 160 ISBN Agencies worldwide, and each ISBN Agency is appointed as the exclusive agent responsible for assigning ISBNs to publishers residing in their country or geographic territory. The United States ISBN Agency is the only source authorized to assign ISBNs to publishers supplying an address in the United States, U.S. Virgin Islands, Guam and Puerto Rico and its database establishes the publisher of record associated with each prefix.
Once an ISBN publisher prefix and associated block of numbers has been assigned to a publisher by the ISBN Agency, the publisher can assign ISBNs to publications it holds publishing rights to. However, after the ISBN Agency assigns ISBNs to a publisher, that publisher cannot resell, re-assign, transfer, or split its list of ISBNs among other publishers. These guidelines have long been established to ensure the veracity, accuracy and continued utility of the international ISBN standard.
As defined by the ISO Standard, the ISBN publisher prefix (or "root" of the ISBN) identifies a single publisher. If a second publisher subsequently obtains an ISBN from the assigned publisher's block of ISBNs, there will be no change in the publisher of record for any ISBN in the block as originally assigned. Therefore, searches of industry databases for that re-assigned ISBN will identify the original owner of that assigned prefix as the publisher rather than the second publisher. Discovering this consequence too late can lead to extensive costs in applying for a new prefix, re-assigning a new ISBN, and potentially leading to the application of stickers to books already printed and in circulation.
If you are a new publisher, you should apply for your own ISBN publisher prefix and plan to identify and circulate your books properly in the industry supply chain. You may encounter offers from other sources to purchase single ISBNs at special offer prices; you should be wary of purchasing from these sources for the reasons noted above. There are unauthorized re-sellers of ISBNs and this activity is a violation of the ISBN standard and of industry practice. A publisher with one of these re-assigned ISBNs will not be correctly identified as the publisher of record in Books In Print or any of the industry databases such as Barnes and Noble or Amazon or those of wholesalers such as Ingram. If you have questions, contact the US ISBN Agency for further advice.
Did you catch what this statement above says? Basically, the company that publishes your book, forever will be the official publisher on record. YOU CANNOT TRANSFER THE ISBN, and YOU CANNOT BUY THE ISBN FROM THE COMPANY, no matter what they say. The book is linked to THEM, not to you. If you want to break your contract with the publisher for whatever reasons to go to a different company, the book will still be registered to the first company. To unlink the book you'll need to get a brand new ISBN and start from scratch: your marketing efforts done earlier will be for naught.
Another common problem with vanity/subsidy publishing is that usually the author doesn't own the cover, the typesetting, the illustrations -- none of the physical files. If you want to leave this company for whatever reasons, you will walk away with nothing. The book will need to be re-typeset and a new book cover designed, as well as obtaining a new ISBN.
Ron Pramschufer, a self-publisher, writes an article about this HERE.
Deciding to go outside of a traditional publisher is a serious decision that must be carefully evaluated. You need to realize from the start that the odds are severely against you, especially for marketing fiction. These two landmines I discuss today are a few among many as you start to look into producing your own book.