Here are my observations:
Your projectile will only ricochet at most twice off of any objects that are not monsters. That includes walls, lamps and other doodads that you would expect shots would/could ricochet off of. The initial shot will go as far as it can until it hits a surface (or it leaves the screen, can't tell for sure). For each ricochet, the projectile will only last for a certain distance. I'd say the distance between you and the edge of the screen (when oriented "straight" and not in the isometric perspective).
Your shots actually go through monsters dealing damage based on your weapon(s) DPS and skill level of your ability. It does no damage to you or your allies whatsoever.
Using it can be somewhat difficult. Targeting a monster will not necessarily hit it, the path your projectile takes will always be in the direction of your cursor. It is more effective if you shoot toward a flat wall. Any irregularities on the surface will cause it to ricochet more essentially stopping it.
It is most effective if the monsters are lined up and you shoot straight through them all. Or, even more so if they are against a flat wall or in a corner. The additional ricochets will deal additional damage.
It is not so effective if there are many doodads on the ground (blocking your shots) or if you are surrounded out in the open.
Make sure you have plenty of mana potions ready or mana stealing weapons, using the ability can drain your mana pretty quick.