The criticism I heard rings true.  It just tries to introduce too many complex characters and thus does not really do justice to any one of them.    The general argument is that Butcher should have either done this book with fewer characters -- or begin with smaller scale story to introduce well a number of the characters first and then bring the remaining characters in during the course of book 2 or 3.  Based on how diverse the characters are, I would have thought a split story in book 1 (like he did in the fury series) would have worked well. 

Some misunderstandings here are the Arbiter position.   

To be an arbiter, you must be an member of the accords.  Which means either you are a representative of a supernatural nation or a individual freeholding lord like the Archive or Marcone.   By definition, you are either a power, or backed by a power in the supernatural community.

In this context, the arbiter will enforce the conditions of the arbitration.  By that I mean Keep the Peace while negotiating and/or enforcing the terms of a dual.  In this they are backed up by the weight of public opinion (at least the public opinion of the other accorded powers) who have an interest in enforcing the rules.  This is a dangerous commitment at times, which is why many of the lesser powers do not try to act as arbiters. 

The arbiter is NOT signing up to enforce the agreements that are the result of an arbitrated negotiation.  In the real world, if the US hosts peace talks between France and Vietnam, they are not signing up to force the two participants to do what they promised to do.   The supernatural world is no different.   

If Marcone is hosting the peace talks, then all he signed up to do is provide a suitable venue, protect the participants and severely punish/kill any that disrupt the peace talks (in some way contrary to the agreed procedures).  That might be a commitment beyond his capability to deliver on, but the presumption is that --- as a free standing lord - he can deliver it.  If he fails, his status as a free standing lord would be put at serious risk.  Of course if he succeeds, then that also lends a lot to his reputation.   

Ok there are a whole lot of assumptions people are making behind their arguments.   Lets call them out: 

1) There is a human (vanilla) agency that is collecting information on supernaturals  (cannon).  it is part of the library of congress.  There are also mentions of other agencies like the Ventori which are mostly vanilla humans that monitor supernaturals (also cannon)

2) This agency has monitored supernaturals for hundreds of years (thousand of years)

3) This agency has a great deal of knowledge of the supernatural community. 

4) This agency has access to 'black op" resources

5) This agency has some agenda beyond passive collection of information

6) This agency has access to significant amounts of useful magic (directly or via hired help)

These are a lot of assumptions and depending on how you answer them, you get a very different impact on the Dresden world.   I think (historically) that most of these assumptions are wrong. 

My personal assumption would be that this library of congress group has been around for several hundred years.  They monitor supernatural activity, but are NOT part of the supernatural community.   They have a fair bit of information, but probably get a fair number of facts wrong, and are not able to do much in the magic department.  They probably have some texts and some stuff that does magic.   The overall organization is small, but they have "some" informants in a number of places and ties to other organizations like the Ventori.   The advent of the internet combined with the paranet has probably been a boom to them from the standpoint of making a bunch of fairly reliable information available to them.  They are unlikely to have any detailed knowledge of any supernatural nation state or a lot of specific information on magic.   They are NOT seen as a serious threat by the major (or moderate) supernatural nations, although many of these nations know these organizations exist. 

There are a number of comparable groups out there, but not as many as you think.  I think the Ventori are probably more dangerous (and more informed) than all these government or private groups combined.   I do think the effectiveness, size and scope of this organization has increased significantly in the last decade or two as technology really boosted the info gathering abilities of these groups.   I think the actions of the Formor have pushed these organizations to become more of a player (to defend US citizens if nothing else).   

Marcone's sister would be interesting... 

It is a connection, but not sure why it would be interesting.  Harry would have no emotional connection to Marcone's sister, so not sure why that connection would add anything.   Yes maybe it puts Marcone in the position of supporting Kumori, but that is easy enough to do in a hundred different ways.  Finally, Marcone has no history of magical ability. 

I could see Kumori being Maggie's twin sister.  Would throw Harry for a loop when he see's a woman who looks exactly like his mom, and also piss him off that he was never told about her from Eb, who had been protecting the one daughter he had left. 

Possible - but it is more of a physical connection than an emotional one.  It is a blood relative (which is important to Harry) and the appearance might throw him for a loop briefly, but that is it.  But it is hard to argue that the connection would really throw Harry off his game in any significant way.  Also, Kumori is an apprentice while Maggie was a full wizard when harry was born.  Very unlikely Maggie's twin sister would still be an apprentice at age 60+. 



The only reason to create a connection is because that connection has some important meaning to someone critical to the story.  Otherwise it is a distraction from the story.  And since any connection (even the ones I proposed) are pretty unlikely, that connection has to be really important to the story JB wants to tell.   It creates a high bar.   

Interesting theory.   My caution on accepting it is that the grey council should be made up of wizards.   100% wizards.  After all, it is a renegade faction of wizards operating in secret against their own government.   

I recognize that Odin was in the battle at Changes, but nothing but Harry's assumption indicated that the attackers were all grey council.  To me it feels like some grey council members plus important allies.   

The other caution is that Harry did not know anything physically distinctive about the wizards that came to his assistance.   River Shoulders would have been visually obvious as he is much larger than a human. 

Peace talks should define the shape of the conflict in the next few books - what replaces the war with the red court.   I am personally expecting another war to start.  Wars are great from the perspective of the Outsiders as they are a great distraction and prevent concerted action against their interests.     I expect this to be a wider war than the war with the red court - Formor, vampires, and several other nations on one side.     And ideally this war will start in some way that splinters the white council - or at least ideally from the outsider standpoint. 

Marcone did not ask Harry to save the person, so no real favor exists.   Harry could see that Marcone was using Harry to save his person.  Harry choose to do so -- but arguably he would have done so anyway even if the person had no ties to Marcone.  The method might have been different, but the outcome probably the same.