I am using macOS Mojave 10.14.5. Books.app shows 650 MB memory being used in Activity monitor even when it is not opened. I have books of around 110 MB but I haven't used the app very much recently.
I tried opening and quitting the app. And quit the process from activity monitor too. It didn't stop. Then, I had force quit the process from Activity Monitor. It fixed it for some days and now it is back in the same state.
In the "Open Files and Ports" of Activity Monitor,
~/Library/Containers/com.apple.iBooksX/Data/Documents/BKLibrary/BKLibrary-1-091020131601.sqliteis an entry along with
.sqlite-shmwith the same file name.
I booted into Safe mode and worked for about 30 minutes during which the app didn't appear in Activity Monitor. It came back in normal mode after around 2 days.
New find is that, when I open iBooks, another PID of the same app is created with around 50 MB. All the further actions like, opening a book, closing it, networking processes etc affect only the newly created PID. Quitting the app kills the newer PID, not the older one.
What is triggering books.app to start and use that much memory?