A lot of ebook readers have one or more slots for extra storage in the form of removable media: SD(HC) cards (micro of fullsize), memory sticks, etc.

Using an extra card for storage consumes some extra power, and it is probably slower than internal memory. On the positive side a card also usually can hold more data, and multiple libraries can be kept on different cards for easy organisation.

Is there any—not so obvious—advantage apart from extra storage space to store books on such cards?

4 Answers 4


There is one major advantage of using add on cards for storing books, and that is in case the device has problems with some of the newly added books. If you use a card you keep your devices internal memory clean.

Sometimes it happens that you have a faulty ebook, or a half-written one, that confuses the ebook-reader. It is not always possible for the ebook-reader to ignore or delete such files, which means you need to delete them using a PC connection. Because of the confusion, the ebook-reader might not be able to allow even that, which requires restarting or even reinitialisation of your reading device.

I have had this happen on my SONY PRS-700, as well as my BookEen. The latter prompted me:

An error occurred.
Pleas plug the device 
to you computer via USB
to remove recently added files,
or press a key to retry.

(retrying did not help).

Storing books on removable media allows you to remove the card, remove any added—faulty—files using a card reader that is not confused by any ebook internal problems, and have a working device without restarting or reinitialisation.

Another, minor, advantage of using cards can be, that if you use an USB 3.0 card-reader for writing, you will probably have faster writing speeds than can be achieved via a wired connection via the ebook-reader (often USB 2). Given the small size of text only ebooks, this might not be notable too much unless you re-write your whole library.


Additional advantages (on top of the 2 excellent ones listed in @Anton's answer) are portability and storage space.

  • If you switch between 2 readers, you can swap in the card (assuming the format and the files are compatible between them) from old reader to the new without having to download the book collection to the new one. As a matter of fact, if the devices accept compatible cards (e.g. FAT formatted SD or MicroSD both) you can re-use the card to read books on an e-reader and another device like a smartphone.

    Also, if your reader goes belly up and dead, you can take out the memory card and move the collection to a replacement reader without any hassle.

    Or, you can loan your books to a friend if DRM lets you, without transfering files.

  • While not a big factor for some people, those with really huge collections of e-books may find internal memory on any book reader insufficient to store their entire collection (especially those who import huge technical manual PDFs etc...).

    Memory cards typically have higher storage capacity than internal memory of the device and thus can store a lot more books.


I put MP3 files to the external memory card and books to the internal memory. MP3 files are usually bigger than books, so a faster card reader can save some time when I reorganize my music library. Books are changing not so often.

Once I have a similar issue as @Anthon mentioned but with a faulty MP3 file on my Sony PRS-650. (I have solved somehow the issue without reformatting etc.)

Furthermore, scanning 8+ GB of new MP3 files takes lots of time on PRS-650 and I don't always want to wait for it, so I could remove the SD card from the slot if it's annoying (or freezes the ebook reader).


Once in a job interview we talked about how I improve my skills and I mentioned that I have an ebook reader. After a while I showed them its book database. I think it was a plus that I could show that I actually read that Java books (and lots of other books, some of them related to their field in the industry) but some books could have been on a removable device because of privacy reasons.

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