FIrst of all, read Mae Brussell. And listen to her shows. Be greedy. You want to start understanding the American republic, she left you a treasure trove of information to start with. You can start with The Essential Mae Brussell.
Second, you can check out Edwin Black's brilliant article, "The Chicago Plot." This is the best single reason I am lukewarm to all the LBJ-is-the-mastermind type books.
If you are starting fresh, these are great places to start: Accessories After the Fact by Sylvia Meagher, False Mystery by Vince Salandria, JFK and the Unspeakable by Jim Douglass, Into the Nightmare by Joe McBride, Destiny Betrayed (2nd edition) by Jim DiEugenio, The Last Investigation by Gaeton Fonzi, Understanding Special Operations by Dave Ratcliffe, and The Devil's Chessboard by David Talbot.
You could also start with - ahem - my zine, An Intro to the JFK Assassination.
Also recommended: Reclaiming Parkland by Jim DiEugenio, Presumed Guilty by Howard Rothman, History Will Not Absolve Us by Marty Schotz, On the Trail of the Assassins by Jim Garrison, The Man Who Knew Too Much (Lachy Hulme edition) by Dick Russell, Breach of Trust by Gerald McKnight, The Oswald Affair by Leo Sauvage, Survivor's Guilt and The Not-So-Secret Service by Vince Palamara, The Echo from Dealey Plaza by Abraham Bolden, Deep Politics and the Death of JFK by Peter Dale Scott, The Killing of a President & The Search for Lee Harvey Oswald by Robert Groden, Oswald: Assassin or Fall Guy? by Joachim Joesten, The Assassinations by DiEugenio and Lisa Pease, Dirty Truths by Michael Parenti, JFK the Book of the Film, by Oliver Stone & Zachary Sklar, The Secret Team and JFK by Fletcher Prouty, Spy Saga by Phil Melanson, and The Zapruder Film by David Wrone.
Recommended, but not as your first JFK book: Harvey & Lee, by John Armstrong. Anything by Harold Weisberg, whose writing style leaves something to be desired although his books have great information. If you get into Weisberg, I actually recommend starting with Case Open, which flows fairly well. All of the Penn Jones Forgive My Grief books, although he is much beloved by me. Assassination Science and Murder in Dealey Plaza, edited by Jim Fetzer, both have fine essays in them - especially by David Mantik and Vince Palamara - but Fetzer has since gone off the deep end, so I can't use these books for citation and don't recommend them to an unseasoned researcher.
Gee, what about these famous books?: I don't really recommend Mark Lane until you've read some other, better books. If you want to know why, you can hear this interview with me I did on the Midnight Writer News show. Same with Tink Thompson's Six Seconds in Dallas, despite some of his good work in that book. He undermines much of his own book in the final passages and has later taken actions that are extremely suspect. John Newman's first book JFK and Vietnam is worthwhile, but be careful. Also be very careful with anything he wrote after that; I'll let Vince Salandria explain why.
Read this instead of that: Anthony Summers wrote a pretty good book called Conspiracy, and then twenty years later he rewrote it and watered it down and called it Not in My Lifetime. Read the first version.
Good books that aren't assassination books per se: Thy Will Be Done, by Gerard Colby and Charlotte Dennett, and all of the Doug Valentine books, especially The Strength of the Pack and The CIA as Organized Crime.
Your mileage may vary: Family of Secrets by Russ Baker, Mary's Mosaic by Peter Janney, Dr. Mary's Monkey by Ed Haslam, Our Man in Mexico by Jefferson Morley, Crossfire by Jim Marrs, Coup De'tat in America by Weberman & Canfield, anything by Joan Mellen or Walt Brown.
The guy I kind of like that most researchers don't: Harrison Livingstone either co-wrote or stole High Treason with Bob Groden (depending on who you ask) and then also wrote several other books, including High Treason 2 and Killing the Truth. I personally find Killing the Truth very entertaining and often hilarious in his observations about other researchers, particularly David Lifton. But I don't cite the research, no.
Disinfo but kind of interesting: The Torbitt Document, Farewell America by James Hepburn.
Disinfo: Reclaiming History, by Vincent Bugliosi, Case Closed by Gerald Posner, Best Evidence by David Lifton, Contract on Amerca by David Scheim, Inquest by Edward Epstein, False Witness by Patricia MacMillan, JFK the Man and the Myth by Victor Lasky, A Cruel and Shocking Act by Philip Shenon, The Dark Side of Camelot by Seymour Hersh, all of the Noam Chomsky output on the subject, any book by Dale Meyers or John MacAdams, any book that relies on Judith Exner as a source for anything that's expected to be true. I also think Larry Hancock is disinfo, which will shock some, but take a look at the two books he cowrote about MLK.
I published 'em, so take it with a grain of salt, but these are both essential or I wouldn't have published 'em: Judge for Yourself by John Judge and The Deep State in the Heart of Texas by Richard Bartholomew.