just read the summaries at the beginning of each volume. But you should really at least read pages one and two of Volume 2. This is where Mueller lays out the four most important things one has to understand about their "findings""
1) because Justice has a rule that a sitting president can not be indicted, they knew that it would be purposeless to come to a recommendation of charges against trump if they fund basis for doing so. So they had no intention of doing so, no matter what they found.
2) because the prez could not be indicted it would not be fair to come to conclusions about whether he SHOULD be indicted, whether he committed crimes. So their intention was just to present the facts without conclusion as to probable guilt;
3) Regardless of the above, they were determined to collect the facts, and create a record of whatever evidence they found, because if they did find something , he won't be prez forever
and 4) if they did NOT find any evidence that he might be guilty of a crime, they would say THAT. But they can't say THAT. In fact they made a point of saying they could not exonerate him.
And then follows all the shit they found. The stuff that now over 800 former or current prosecutors across both parties agree he should be charged with.