Our colleagues at were tipped by a reader that Amazon has finally released its . The  appeared a year ago, and a Windows version followed last November (see " ," 3 March 2009). The free Mac OS X software is currently numbered 1.0.0 Beta 1.
Amazon also released for an iPad app.  last week that iPad apps submitted by March 27th would be considered for release in the App Store on the April 3rd iPad ship date. Amazon seems ready for this.
Amazon coyly names its iPad product page "Kindle Apps for Tablet Computers," followed in smaller type by "Including the iPad." The app sounds quite similar to the Mac OS X and iPhone apps with additional controls. (The language Amazon is using may be part of negotiation with Apple about including iPad details, or its own way of stressing independence from Apple's hardware.)
Both the Mac OS X program and iPad app let you read and retrieve any books that you have purchased via the Kindle Store or from a Kindle device using the same Amazon account. Subscriptions to newspapers, magazines, and blogs - available on Kindle hardware - aren't included, which is true of the Windows and iPhone software as well.
Both the Mac OS X and iPad app let you adjust a book's display to a greater degree than the iPhone app. The Mac OS X program lets you choose among 10 type sizes, although only in the Georgia typeface. You can also control the column width to aid in legibility, but not the vertical space between lines, which is set in lockstep with type size.
The iPad app will let you adjust the background color and set backlighting brightness in the app in addition to vaguely described "font size" customization. The app will also use a page-turning animation (which can be disabled) that resembles what we saw in Apple's iBooks app at the iPad launch.
The iPad app will let you set or remove bookmarks, highlight text, and create notes, just as. The Mac OS X software lets you manipulate bookmarks, but only view notes and highlights. Amazon  that a "near future" update would enable note creation and highlighting.
Amazon's Whispersync service works with all its software, tracking and restoring where you left off reading, as well as keeping annotations, notes, and bookmarks up to date.
No mention was made of text-to-speech in the Mac program, which is a feature (and minor selling point) of the Kindle 2 and Kindle DX, but which proved rather controversial (see "," 2 March 2009). In theory, it should be easy to implement on the Mac, using Mac OS X's built-in speech synthesis capabilities. Neither the iPhone app nor the preview of the iPad app mention text-to-speech, either.
A little secret of the Kindle Store is that publishers make quite a few books available at no cost, which lets you test out the software for reading (as well as get some great titles for free). will show you all Kindle books sorted by lowest price first, which starts at $0.00. You can then click into subject categories from the left navigation bar to narrow the search.