The
GitHub issue template will detail how to enable verbose debug logging

.
Given your lack of input, though, you might instead want to manually edit
koreader/koreader.sh over USB (in a decent enough editor that won't mangle unix line endings), to add
-d -v to the reader.lua invocation; i.e., replace line 398 with
Code:
./reader.lua -d -v "$@" >>crash.log 2>&1
Note that this miiiight be fixed in current nightlies, but I'm still mildly curious about seeing logs in your current state

.