I’ve actually written four official supplements for Ars Magica 5th edition, but as of Feb 2013 only one has been published and released. Due to the NDA agreement authors sign with Atlas when starting a project, I can’t actually comment directly on any of the books until they are released and sighted in the wild (this has come to mean when someone announces and proves that they’ve bought a copy on the Atlas Forums). There’s quite a period between handing in the final draft and seeing it released as a printed book unfortunately, but it’s worth the wait.
Click on the cover(s) below to access my comments (if released) or the official webpage (if still pending release).