This topic lists the Bible Apps I have on my own smartphone and tablet and recommend to others. It's a short list because I spend most of my day on a PC and have access to lots of online Bible stuff. But the following two apps are great when I'm traveling or away from my PC.
I like "free" apps, and use them for limited purposes (like a quick look up). When I'm going to do a serious study, I used online tools on a bigger screen. Some Bible apps for adults make their money by selling you add-ons.
You are welcome to recommend the ones you like and use.
Related Topic: Bible Apps for Children!
Bible Gateway's Bible App (totally free)
I used www.biblegateway.com as my go-to online Bible, so it's nice to have their app on my smartphone when I'm away from my PC. I also like the fact that it has ALL the various translations I consult --for free. Some other Bible apps charge you for certain translations. Through the app I can also access some of Biblegateway's study tools and dictionaries. You can also use the app to LISTEN to the audio of the Bible, which is a nice feature if you are driving. You can select the style of reading too, like "dramatized" that has some background music.
Screenshot of biblegateway app's "audio" playback options screen of any text in the Bible.
The BlueLetter Bible App (totally free)
I'm a Bible word study geek and love to look up the original and various meanings of keywords in a Bible passage. The Blueletterbible.org's website is what I use when I'm on my PC and the APP version looks and works the same way with all the content I expect to find. See my article about how word studies can stoke your lesson creativity.
Look for the iPhone/iPad and Android versions in your App Store or on their app page here. They have other apps on that page which I'm not recommending at this time, but might be nice.
Here's a screenshot from the blueletterbible page showing links to keywords in the Genesis 1 text that I wanted to look up. Did you know that the word "hover" in Hebrew can also mean "dance"?
Screenshot from the app. You open a text and tap it to access the Strong's Concordance (word study) resources.