A couple weeks ago, while I was in the middle of the first draft for Book 06 of Iyetra, I realised I had made a very grave error and left something important out of the now-published version of Book 05. One of the established rules of the Iyetra universe is that magic-users need to have a catalyst on their bodies at all times in order to focus and use their abilities (or be on one of the Advent cities that have a system of magical-energy-repeaters set up to negate the consequences of this restriction.) I wrote, re-drafted and revised the entirety of Book 05 without realising that I'd never equipped one of the main characters with a catalyst and thus defied the physics of my own universe.
Forgetting this was reasonable, I suppose — a year passed between the publication of Book 04 and my first day starting the first draft of its sequel — though it was unfortunate it didn't come up in review by my editors. However, we're all human and these things happen. In any event the mistake was made and worse had been out "in the wild" for months before I caught it.
In the old days of book publication, this sort of thing had little in the way of a solution. Once printed copies were produced there wasn't much that could be done to correct mistakes after the fact, and you were even more out of luck once books went on sale. If an author was fortunate and sales merited the reprinting of different versions (hardcover to paperback, anniversary or second/third/etc editions), longstanding issues could be corrected eventually but sometimes this could introduce its own, new errors.
These days, and with my particular luxury of the Iyetra series existing so far in only ebook format, fixing this mistake was just a few minutes' effort to write new text, patch it into the original "final" draft, and submitting new digital files to Amazon, Kobo and so on. Twenty minutes later the issue was resolved almost as if it had never happened.
Infrequently, I receive emails from storefronts like Amazon letting me know a title I'd previously purchased had done something like this — whether because of a publisher correcting typos from OCR scanning or something more, books are increasingly less of a fixed format than they had been previously. The Apple iBookstore now even offers version numbers and "what's new" updates for publishers and authors who want to highlight these corrections in the same way software developers have clued customers into patch changes for ages.
In some ways, this reflection of ebooks-as-software makes it easy to fix issues that might have otherwise left a reader unhappy with a purchase, but it seems like it could be easy to fall into the trap of the "we'll fix it after launch" syndrome that plagues many games coming out in recent memory.
Still, it also provides an interesting playground for using ebooks as more than just digital constructs that emulate a physical form. It could be interesting to release part of an ebook that receives regular, free content updates over time, or even a book whose author drastically rewrites and changes whole sections of the plot after release. Something like this could be advertised as the reason for following the title in the first place — pushing a reader into paying attention to the book from the start, otherwise leaving them missing out on experiencing content after the author eviscerated it from the digital file. In that respect, the book becomes less of a static medium and more like a movie or television show; something that is created and destroyed over time instead of sitting in one fixed format after going on sale.