I just received my new Samsug Galaxy S4 today. I've been running the android platform on many devices for years, but the last phone I had was a Windows phone (Interface blows the android away), but not being mainstream enough, our carrier is dropping it, so I had to switch. Most apps are ported cross platform so it doesn't matter if you have a droid or Iphone or winphone etc. But there are a few specific to each platform. My old old old reader device is having some battery issues (It's 8 years old now), so I'll be porting all my PDF's etc over to the phone on a micro SD card. I've always kept most apps as "Static" apps, or reader/information apps. Just so when I run across something I don't know about, or I need specific instructions that have not been memorized I can pull them up quick. (Regardless of data connection). Like having an entire library of survival books in your pocket any time you need them.
I'd have to say a good PDF reader is the first key app.
I was using the basic free app "PDF Viewer" that came with my asus tablet, but lately I've been using the kindle app for PDF viewing. I like it a little better on the larger tablet, but will find out on the phone in the next couple of days.