The idea is not bad. BaaS is on its way actually: there is many editions (updated) of the same book.

The problem (especially in IT):

Well, I see books evolving the same way. Or, at least, non-fiction reference books. Think of all programming books published out there. With a few notable exceptions, most of them become obsolete soon after printing. Once the book gets out, the publisher pays off the original investment; the author receives royalties from every sale, which continues for a while. A few years later, the technology landscape has changed enough to justify publishing a whole new edition. But it is a considerable investment risk for all sides.

Leanpub and Gumroad are 2 platforms that encourage to update the contents of the books.

The deal is to write a little content of the book that is sold for nothing or nearly nothing. Then the writer see if there is enough value into adding content. The readers that have bought the book early will have access to the future content too.