Really good design. Parallel bibles feature is the key for me - I use Russian and NET for modern English. Text and audio commentaries including Chuck Smith are awesome. Custom search of specific books or the whole Bible is great. App support is very good - these are Christians serving Christians!
What could they add? Non canonical books, maps, an option to download more modern English bibles NKJ, NLT, ESV, NIV. Other languages and translated book names: Modern Russian translation by IBS, Estonian, Kazakh... Fix parts of the Russian Bible in the parts of prophetic books of the OT where text was garbled. But for free I am happy to keep as is.
God bless the developers and their ministry!
Сhelovek iz Pitera about Blue Letter Bible, v2.59