The class struture allows nearly any combination of characters to be effective since every class has access to abilities that enhance their skills and their combative ability. Book worm adepts can weild chain axes or handle a long las, a Guardsman can have learned a thing or two about Forbidden Lore or the workings of the great Adeptas.
This is because the two prime focuses of the game are investigation things and killing things. These tasks can be done in either order and are often considered interchangable by the Inquisition.
I'd like only one of each class but players are free to select as they wish.
Quick class summaries are:
Adept- Lots and lots of lore abilities.
Arbitrator- Good weapon and social abilities.
Assassin- Lots of ways to kill things.
Cleric- Good social and combat abilities.
Guardsman- Good access to weaponry abilities and alot of Hit Point boosts.
Imperial Psyker- Psykers have access to power psykic powers and good weaponry options. Slight warning: psykic powers can have side effects such as headaches, blasting your friends, or demonic beings errupting out of your orifices.
Scum- Good social skills and a wide range of abilities.
Tech Priest- Access to information and abilities beyond other classes, very low fellowship ability.
I would also like to recommend
this website for it's character generator.