Carpentry and Woodworking - bookcase and wood floor issue

the question I am going to ask is regarding the wood floor and my bookcase. I just bought 2 big bookcase from IKEA. After I put them up along the wall, I found they aren't align with the wall. It seems the wood floor is not even. I know I need to screw a L shape steel bracket( top of the bookcase) TO the stud. But is there anything else need to be done? If I put some shims on the bottom of the bookcase, will the trims put a permanent mark on the floor?

What is your suggestions?

Welcome to the forums! When you say they aren't aligned with the wall, do you mean from side to side or front to back? Did you remove the baseboard from the flooring? You will need to do that and cut it and replace the smaller pieces on either side, so the unit will sit flush to the wall. Place a framing square around the corner of the unit to see if it is square. It possibly is not. But definitely put some sort of "L" bracket to keep it from tipping.

What Chandler said. You can cut out the baseboard, or cut the bottom of the shelf unit to fit over the baseboard. But the unit should sit flush against the wall. Shim as needed at the floor, and DO add a bracket at the top to prevent tipping.

It appears your assuming the floor isn't level, are you sure its not the wall that isn't plumb? Irregardless of the wall, teh bookcase needs to sit level.