After having already arrived on a host of Android slates, iPads and even TouchPads, Zinio's reader app has now made its way to the newest tablet platform -- the Kindle Fire. The magazine marketplace made its debut on the Amazon Appstore today, just in time for today's grand launch. Available as a free download, Zinio brings more than 5,000 magazine titles to Amazon's new slab, including The Economist, Rolling Stone and US Weekly, among others. New subscribers, meanwhile, will benefit from an extra $25 in credit, redeemable through March of 2012. Find more specifics in the full PR, after the break.