Nimble books, who publish a range of navy related works, have released a free iPhone and android app that includes frequent extracts from their back catalogue and future releases. Don't know how to link directly to it, but in your phones App Store just search "Warships and navies" or Nimble Books.
I cannot find a quick link to the full back catalogue you can get a feel from visiting https://www.nimblebooks.com/index.php/
I cannot find a quick link to the full back catalogue you can get a feel from visiting https://www.nimblebooks.com/index.php/