i'm using newest elementary os with my lenovo x250 and after i installed calibre from app center it just doesn't open. I click on the icon from Application meniu and nothing happens. Help would be appreciated.
Try installing it manually. This isn't really the fault of EOS, Calibre say themselves
Please do not use your distribution provided calibre package, as those are often buggy/outdated. Instead use the Binary install described below. I'm guessing that's for a reason, and their old packages often don't work well, or aren't given back-ported updates.
sudo apt-get remove calibre should work
Then visit this link to get a binary installer of latest version.
Hope the manual install works. If it still doesn't, let me know.