The "Sofia City Guide" is an info guide with useful information about the city. In fact, it is a small travel guide for the city itself, covering all the major "Highlights". Every month there is a new edition, so the information is very up to date. It also covers the festivals and important happenings that month.
The printed version can be found in every major Hotel in the town.
If you want to prepare yourself before, there is also a website giving the same information, plus some more. The website can be found at:
http://www.sofiacityguide.com