It is nice to be able to have your music and books accessible anywhere in a portable device such as a smartphone.
Windows smartphones serve very well for this purpose especially now that they are very cheap.
These phones typically have the capability to plug in extra memory and hold a huge library of music and books.
It takes some doing just to set them up for the job.
The most straightforward way to get content onto the phone is to use a Windows computer.
The Windows phone appears as just another directory on the PC once connected by cable.
Having the Windows Phone recognise the same content is something else.
I found just two apps which worked well for music, one of them VLC and the other Cool Reader. The files should also play from the Files app.
I found no way to play Amazon Cloud Music. Google Music played online through the Groove app.
Books are another matter. There was no problem downloading them direct or transfer from a PC, as with music.
Using the Kindle books app on the smartphone also gave the capability to download to read away from Wi-Fi.
It was necessary to use an app called Gooreader to read Google Books online and they could not be read offline.
A paid version of Gooreader could be installed on a PC to extract books from Google Books for transfer to smartphone. Better not to bother but simply to download the books on PC and transfer them.
If you transferred documents into either Amazon or Google Books these are not accessible on a Windows phone either online or offline.
There are plenty of reader apps to access and download ebooks elsewhere. A prominent app is FB reader.
Once setup you have all your music and books available in a small package offline anywhere you go.