Forgive the snarky title, and I shouldn't be surprised by this, but I'm encountering a lot of frustration when trying to find decent books on the assassination of JFK that don't immediately dive into conspiracy with aplomb.
I'm fine with books that focus on the conspiracy bits as an aside or that interrogate them historically, but the vast majority of the ones I've come across have sounded like lesser Oliver Stone movies.
I recommend two. 1) Gerald Posner's Case Closed, and 2) Vincent Bugliosi's Reclaiming History. Both of them are big books trying to cover all the details: Posners is over 500 pages and Bugliosi's is over 1,600.
I like Bugliosi's better. And that does annoy some people, as Buglisoi himself was not what you would call a mild-mannered reclusive scholar: he had been a trial lawyer and a prosecutor. His writing style is hectoring and abrasive, and at times when reading the book you very much feel as though there's a lawyer loudly making a case. He was not someone I think I would have wanted to hang out with. But he makes the invaluable point in his book that it is very common for many criminal cases to have some inconsistencies in some of the details, including the JFK assassination, but unusually in that case many theorists seized on those details to deny the greater real facts in the case.
Posner's tone is more neutral, and he has more interviews with important figures in the case- which you would expect from a good investigative journalist. If you have the time and can stand the writing style, check out Bugliosi. if you have less time and tolerance, read Posner.
EDIT I should add, that the JFK assassination is a commonly asked question, and so there has been some good stuff posted about it before, over on the FAQ: https://www.reddit.com/r/AskHistorians/wiki/us_history