Now that I have had the chance to review this more thoroughly, it is much more disturbing. I promised a brief legal analysis earlier, and I am going to attempt one now, with two caveats: First, this is a "summary" of the Mueller report, written by a partisan (so there is more to come); second, I can only address what is in the summary, which has been made public (I'll be interested in comparing these thoughts with what eventually comes out). BLUF: Barr did what he was appointed to do, and that was to cover for the President. This is a very political, not legal, document. Let's get to the details:

1) Barr did not quote a single full sentence from the Mueller report, so, we really don't know what the edited determinations really were. This is cherry-picking at its highest level.

2) the wording of the quotes that were provided are curious, and significant. The quotes:

a) [T]he investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities. First, notice that this is an excerpt of a quote, not the actual sentence from the report. What is missing is as important as what is there. Second, "did not establish" is legal jargon for "probably could not prove beyond a reasonable doubt." In other words, there was probably substantial evidence and the first missing part of the sentence likely laid out the evidence that supported collusion. Barr has elided this for a reason. In the fullness of time we'll discover that reason.

b) Coordination [is defined as an] agreement tacit or express between the Trump Campaign and the Russian government on election interference. This is the definition Mueller (apparently) used. What it says is that there was no direct evidence that coordination took place, but there were "coincidences" that suggested it. Again, what is missing here may be more important than what is included in the "summary".

c) Mueller determined not to make a traditional prosecutorial judgment about whether the president obstructed justice over the course of the two-year investigation of Russian interference in the election. Instead, Mueller laid out the relevant evidence on both sides of the issue, but did not resolve what the special counsel saw as the difficult issues of fact and law concerning whether the Presidents actions and intent could be viewed as obstruction. Muellers report does not conclude that the President committed a crime, it does not exonerate him. This is a doozy of cherry-picking and covers up more than it exposes. What Mueller apparently concluded was that while this report does not conclude that the President committed a crime, it also does not exonerate him. What were the "difficult issues"? Which "actions and intent"? And, that brings us to the primary purpose of Barr writing this letter, and being appointed in the first place:

AG Barr concluded that the evidence developed during the Special Counsels investigation is not sufficient to establish that the President committed an obstruction-of-justice offense. This was not Mueller's conclusion, nor really anyone else's. It is consistent with the memo he produced that got him the job as AG. As one observer pointed out: "Crucially, we dont know whether Barr concluded that the president didnt obstruct justice or that he couldnt obstruct justice." The latter was the premise of his unsolicited memo. It is this conclusion that is most suspect in the summary and will still be litigated in the future. Barr is not in the mainstream on this one.

3) Was Mueller really done? I admit I have been suspicious for some time that the Mueller probe was concluding not because he was finished, but because the new AG was demanding it. The circumstances of the release, the summary, and the language bolsters that suspicion. Mueller is a famously thorough investigator and prosecutor. Some of the language of the summary also suggest that - they are acutely defensive and excessively laudatory of the thoroughness of investigation - and the fact that Mueller didn't reach a "conclusion" on the fundamental question of obstruction.

4) Is this a legal document? No, not really. The Special Counsel is required to provide a confidential memo to the AG. The AG is now "summarizing" that memo for Congress - but it is abundantly clear that this summary is excessively slanted toward a predetermined conclusion (hence the quick turn-around). This is a cover-up memo intended to "set the stage" for future disagreements, and slant coverage for now. I am even more suspicious of Barr's motives than I was before, and it was obvious to any observer that this is exactly what he was hired to do. When the Mueller Report actually sees the light of day, I will bet significant money that it looks radically different from this "summary".

[Since I went to bed last night, lawyers have jumped in all over the internet with similar analyses, e.g.,
Barrs Startling and Unseemly Haste
(The Atlantic);William Barr Did What Donald Trump Hired Him to Do (Slate); What to Make of Bill Barr's Letter (Lawfare)]