The main drive of the civil war was to be able to keep their slaves (the south) and they wanted it to be a state to state issue, not federal. Lincoln and the north wanted it to be dictated on a federal level (which is where a lot of the anti Lincoln sentiment comes from, I'm guessing) and Lincoln tried to avoid war to settle it. But when the south basically forced their own government, war was inevitable.
So yes, the war was about slavery and the rights of the states (south) and the rights of the federal government (north) and who would control it. A lot of pressure was on Lincoln to free the slaves, which he did not initially intend to do, but it became a bigger issue than he wanted.l, so was forced to.
The bottom line is the war was about states rights and them wanting to control their slaves at the state level.