According to this site, "The National Archives and Records Administration is releasing documents previously withheld in accordance with the JFK Assassination Records Collection Act. The vast majority of the Collection (88%) has been open in full and released to the public since the late 1990s. The records at issue are documents previously identified as assassination records, but withheld in full or withheld in part." A first batch of 3,810 records from the FBI and CIA were released in July of this year. While I read about the release in the news at the time, I have not heard anything about the contents since. Was anything interesting or significant found? The issue is in the news again today with the impending deadline at the end of this month for the final release of all the records.
Follow-up question: were there any big bombshells in the original release of the first batch of records in the 1990s which changed common thinking about the assassination?
Can anybody recommend a solid, well researched book on Kennedy assassination ?
To add on: as laymen are there historic detailed questions that would be fruitfull to ask? How could one make the best out of the declassification? And what will be worthwhile to look for in the debate on the new material in relation to old historic questions?
I'm disappointed that no one has addressed OP's initial question. Is there any expectation that the new files will bolster any of the theories behind the assassination? Did the earlier release of files add anything new?
If we are talking, what's the historians view on JFK and the Unspeakable: Why He Died and Why It Matters by James W. Douglass? I tried to ask here but didn't get much.
Is there any truth to the allegations that some of the files have gone missing?
So this has been sitting for a day now, and I was hesitant to weigh in because, well, this isn't my area of study, to say the least, but I do think there are a few things which can be noted nevertheless. For the documents released in the 1990s, I really can't say anything specific on what they revealed, but any reputable work on the history of the assassination that has been published in the past 20 years will likely have incorporated them already, and there might have been bombshells at the time, but by this point that'd be old news, and someone on the younger side might be surprised even to learn that some of what was revealed only came out so late. Certainly, it can be said that the broad narrative - Lee Harvey Oswald was a single gunman, firing from the book depository - has never been impeached, and nothing that came out then did so either.
Now, as for the 2017 documents? Well, as you note, some were released in July, and more will be coming out by the end of the year. Politico did a write up just after the first patch a week after they came out, and I think that their summation provides us with a few important points. Namely... don't expect anything to happen too quickly! At the one week mark, as they note:
JFK historians and the nation’s large army of private assassination researchers are still scrambling to make sense of the latest batch of tens of thousands of pages of previously secret CIA and FBI documents.
Which is to say, it is a ton of material. A lot of it is also useless. Many documents apparently are nothing more than duplicates of records already released. With the July Batch, nothing came out which was a bombshell. The core narrative remains essentially unchanged. There does seem to be some interesting material concerning internal communications of the CIA about their concerns of missing some key connection - the possibility Oswald was connected to Cuban elements in some way seems to loom large - but that is only speculation. There were some clues which they feel the Warren Commission didn't investigate thoroughly - a trip to Mexico apparently wasn't properly followed up on - but there is nothing in these documents which suggest there actually was a connection, only concern for the possibility that they couldn't find one that might nevertheless exist. Their concerns seem, at least in part, to stem from the fear that if that were true, it might have been in retaliation for their own activities against Castro and Cuba. But again, all that that documentation points to is some people in the CIA during the '70s navel-gazing in the wake of the Warren Commission, and in no way points to actual evidence in any way. The key thing that these documents reveal so far, to again repeat and this time give it to Politico, is that:
None of the files released last week undermines the Warren Commission’s finding that Oswald killed Kennedy with shots fired from his perch on the sixth floor of the Texas School Book Depository in Dallas’ Dealey Plaza—a conclusion supported by 21st century forensic analysis—and that there was no credible evidence of a second gunman.
For the documents still forthcoming, we can only speculate what they contain, but the chances of them changing the above are scant, and that is charitable. The best likelihood, if someone is able to really research these trails which went cold a half-century ago, is providing better elucidation into the motives of Oswald. The documents point to others who believed connections might be out there unfound, and maybe there is something to that or maybe not. But any really revelatory information that these might turn up isn't going to show up yet. It would likely take years of further analysis and research before you find any reputable historian publishing a new work, or revising their previous ones, to incorporate these documents even in a relatively mundane way, let alone in a manner which they believe offers new elucidation on the assassination.
TL;DR: There are some tantalizing tidbits at the margin, which with a lot of honest investigative work could maybe let us learn more about Oswald's motives, but Oswald Did It, In the Book Repository, With the Carcano.
In any case, all the documents can be found here. The Politico article I referenced is here. They in turn highlight one of these internal CIA documents here.