Brief: If you are looking for an effective eBook reader for Linux, Bookworm will serve your purpose.
Bookworm is an open-source eBook reader with an easy and simple layout supporting different file formats like epub, pdf, mobi, cbr and cbz. Supporting cbr and cbz files means that you can also use it for reading comics on Linux.
Features

- Supports eBooks in the formats epub, pdf, mobi, cbr and cbz.
- Supports editing the book metadata and filtering.
- Features like zoom in/out, margin set, line width increase/decrease are available.
- Supports different reading profiles of light, sepia and dark. Night mode is also supported.
- Bookmark pages from your favorite book to read it later.
- Supports full-screen mode.
Installing and using Bookworm
Install Bookworm by typing the below command in Terminal:
sudo add-apt-repository ppa:bookworm-team/bookworm
sudo apt-get update
sudo apt install com.github.babluboy.bookworm
Note that the installation did not work with Ubuntu 20.04 LTS in our initial tests. However, you can easily install it on Ubuntu 21.10 without adding a PPA with the following command:
sudo apt install bookworm
In either case, you can also try installing the Flatpak package irrespective of the distro, using the command below:
flatpak install flathub com.github.babluboy.bookworm
You can also explore other installation methods from its GitHub page.
Once you are done with the installation, you can launch it from the Dash search. If it’s your first time, Bookworm will ask you to add some eBooks. On the reading screen of Bookworm, the pages can be driven using the left and right arrow keys and the page number is displayed at the bottom.

There is a “Library” option in the Title Bar which allows you to see your Library, add/delete eBooks, and edit the metadata.
The information (“i”) option gives you an option to see the Table of contents, bookmarks and Search results.
Formatting option (“A”) allows you to set reading preferences like font size, line width, line spacing, and selecting a profile.
Next to it is the Bookmark option, which can you click to bookmark a page while reading any eBook.
There is a search bar on the right side along with a Preferences tab. The Preferences tab gives you options to Turn on Dark mode, Enable Cache, Set font, Customize reading profiles, and add the default folder where you want the app to check for e-books.

The clean UI gives you a distraction-free experience and night-mode support is the one much needed.
If you are looking for places to get DRM free eBooks, I suggest checking Humble Bundle Book sale
Disclaimer: We may get a commission if you purchase something from Humble Bundle through our Link.
Apart from unbelievably low prices, each purchase also supports a charity.
Have you tried Bookworm apps? Which is your favorite eBook reader, tell us in the comments.
Many thanks for giving the spotlight to Bookworm…I’m the developer for the same. I see a lot of comments for issues in installing on Ubuntu with broken dependencies…I developed Bookworm for Elementary OS and it looks the best there…but I have plans to bring it to other distros and Ubuntu is the closest one…people have built it for Fedora and Arch as well…
Apart from the features covered nicely in the article, Bookworm has some shortcuts as well…refer to the same on this website which I keep updated as I go along adding new capabilities: https://babluboy.github.io/bookworm/
Bookworm is very much under development at the moment…I’m trying to bring in better rendering of PDF and add capability like notes/annotation….
Bookworm interface is attractive and functional, the core features just right. However Bookreader makes the same assumption as Calibre – another popular book reader that I do not use. The assumption is the following:
The carefully created file and directory hierarchy for books that the user has painstakingly created can be dispensed with.
Just like Calibre, Bookworm creates a new file system structure by copying books from their original location. This is bad:
1. Duplicate disk space. Does he delete the original copies of the books?
2. If so he will lose the structure he created with loving care.
There is no reason why a book reader needs to duplicate the books. The application simply needs to store the location of the books.
Oh well, back to Fbreader or Coolreader.
Hi..Bookworm only caches the content if the user sets caching in the preferences…otherwise just the location and metadata of the book is stored and every time the book is opened from the library it is parsed and opened for reading….this avoids the duplication of content…
However if caching is turned on then the parsed content of the book is stored to open it quickly for subsequent reading…
When a book is removed from the library the original ebook file is un-affected and is not deleted….