So far ProPublica has been publishing its investigative and data journalism on its own website and through partner news outlets. This week ProPublica launched its own digital magazine -- a strategy worth watching, and perhaps emulating, as the digital (and especially tablet) landscape continues to develop.

ProPublica: The Magazine is a free monthly collection of ProPublica's best reporting on current news topics. According to Nieman Journalism Lab, the inaugural issue focuses on war and gun violence, including stories on drone strikes and the Guatemalan civil war.

So far it's available through iTunes only for iPhones and iPads. ProPublica president Dick Tofel told Nieman that the main point of this venture is not revenue, but rather to expand ProPublica's mobile audience.

This endeavor is a bit like the practice of repackaging news stories into e-books -- something that many news outlets (including some community news sites) have tried or are doing. It allows for thematic organization and can add context and increase the "shelf life" of digital content, compared to in-the-moment news reporting.

Magazine-style content is particularly appealing to tablet users -- and the popularity of large and small tablet computers is growing rapidly. For now, the iPad (both full size and mini) is by far the most popular tablet device, so it makes sense to develop a digital magazine with iOS devices as a primary market. However as Android and other tablets gain market share (especially in the market for smaller tablets, and among lower-income demographics), it will increasingly make sense to develop magazine products for these platforms.

ProPublica's magazine app was built by 29th Street Publishing -- a company that develops apps for other publishers and writers. The app approach to digital magazines also makes a lot of sense given current mobile technology, and the likelihood of offline reading for this market. However, apps also present obstacles to search visibility, link-friendliness, and social media sharing -- which is a problem if your main goal is growing your audience.

As mobile browsers and networks continue to evolve, and the market share of non-iPad tablets continues to grow, it's likely that delivering digital magazines as mobile web applications (viewable through a browser, or third party browser-like apps with offline caching such as feed readers) may become a more platform-neutral (and thus economical and flexible) delivery strategy for digital magazines.