Reddit mentions of Mandolin For Dummies

I started playing in July, starting with essentially zero experience. I started out with a deeply craptacular instrument, and moved up to a decent student-level instrument a couple of months later. And I would second agoatforavillage's advice: it's 100% worth it to get the best instrument you can for your budget. I actually had fun with my cheapo mandolin, but buying my lovely little Eastman A-style has made ALL the difference. In the beginning, one of the most important things is laying down your foundation of habits and technique; and you'll be on much better ground with an instrument that can support you. (And yes, you really do play differently -- I would say, with more technical rigor -- on a decent-quality instrument.)

As for the rest, I picked up a copy of Mandolin for Dummies by Don Julin, and in spite of the title, it's a really solid book for a new player. I also got tuning and metronome apps for my ipad (do not neglect the metronome!), and got a few different picks designed for mandolins. And after that, it's just a matter of putting in some time. :)

And just to note: a "decent instrument" doesn't mean you need to drop $5000 on an instrument; a few hundred bucks, well spent, can get you a very serviceable mandolin that will support your learning for years.