Ok, I resolved my problem
I had to browse system catalog (hidden by default) and delete some state, temp and cache files. I don't know which delete was important but i deleted, among other things:
- wall.cache
- journal.log
- temp files with names of deleted books
Thread can be closed.
EDIT:
OK, got it second time. I had to delete only 1 file:
- system\config\widgets\config\wall.cache
Problem was some damaged epub file I think.