Kindle Format 8 with support for HTML5 and CSS3 is very, very BIG news. Finally, the primitive Mobi7 format with its bizarre and convoluted formatting workarounds will be a thing of the past in a few months.

Amazon’s announcement explains the changes. Their FAQ (at the bottom of the announcement) says that it won’t be necessary to redo earlier books. They’ll still be available for the Kindle Fire and other Kindles. However, for those who are paying attention: "Information on how to update your existing titles to take advantage of new capabilities in KF8 will be in the new Kindle Publishing Guidelines, available soon." Think about that for a minute…you don’t have to go dash your brains out against the nearest brick wall, but the opportunity exists.

My fondest hope is that automatic image resizing "triggers" will stop mucking up the appearance of certain pages without having to redo and experiment. Those of you who have worked with images that need to be approximately half the size of the viewing area, or have seen small images and dingbats quadruple in size, know what I mean. May your About the Author page never again make you look like an egotistical twit with a full-screen mugshot!

In a nutshell:

• HTML5 with CSS3 will enable some nice formatting touches and hitherto forbidden styles that are already familiar in web pages, such as floated elements, embedded fonts, better list and table support, CSS drop caps, and so on. Technical books, cookbooks, and other titles with lots of images or small tables will be more readable. The danger is that some people will throw in everything but the kitchen sink and create truly glarpy books. Of course, they can do that now, but it’s harder to pull off.
• A new version of the Kindlegen and Kindle Previewer tools will be released for those who convert Word or other document-types to eBook format. Kindlegen will accept "a wide variety" of input formats, including HTML, XHTML, and ePub. Does ePub input mean that its NCX file will be automatically "flattened" without editing and work just fine with Kindle?
• New Kindle Publishing Guidelines with instructions on "how to update your existing titles to take advantage of new capabilities in KF8" will be issued. Hoo boy! is this gonna be fun or what!

Essential information:

Amazon’s announcement
List of Supported HTML Tags and CSS Elements

In any case, Kindle (and ePub books) are essentially long web pages, as they have been in the past. The use of the HTML5 and CSS3 standards for Kindle books will make them more accessible on devices and readers and should eliminate some of the worst formatting challenges of the past.