Reddit mentions of The Years of Lyndon Johnson: The Path to Power; Means of Ascent; Master of the Senate; The Passage of Power

This is quite the under-taking, so I'll just list the presidents from which I am familiar with the historical literature. In order to guarantee that you get an analytically thorough understanding of each president, I'll avoid "pop" histories (thus, nothing by David McCullough) in favor of more analytically driven, yet still well written, histories. I will still incorporate some books from non-academic publishers, however. First off, the best place to start would probably be the University of Kansas's American Presidency Series (note that this is different from the American Presidents Series, which is done from NY Times books. Always be sure to check the publisher). This series is great for getting a good understanding of what historians in general have written about each respective president; however, the series only focuses on the presidency, which is more constrained than what you're looking for. I'll just go in sequential order based on when the individual was president.

• George Washington
  
  Washington: A Life by Ron Chernow. (Do not buy this book off the internet. I've seen the hardcover version of this book in the overstock sections of Barnes and Nobles, Wal Marts, and even Albertsons for $6. Don't become reticent about it because it's in the cheapy bin at Wal Mart. Chernow is one of the best biographers of early American history and the book won a Pulitzer.
  
  His Excellency: George Washington by Joseph Ellis
  
  
• John Adams
  
  John Adams: A Life by John Ferling
  
  
• Thomas Jefferson
  
  Thomas Jefferson by R.B. Bernstein
  
  Thomas Jefferson: The Art of Power by Jon Meacham
  
  
• James Madison
  
  James Madison: A Biography by Ralph Ketcham
  
  The Sacred Fire of Liberty: James Madison and the Founding of the American Republic by Lance Banning
  
  
• James Monroe
  
  James Monroe: The Quest for National Identity by Harry Ammon
  
  
• John Quincy Adams
  
  Paul Nagel's John Quincy Adams: A Public Life, A Private Life
  
  For an in depth look at his time as Secretary of State, check out John Quincy Adams: Policymaker for the Union by James E. Lewis, Jr.
  
  
• Andrew Jackson
  
  Robert Remini's 3-volume biography is still the most comprehensive on Andrew Jackson. Vol. I is Andrew Jackson and the Course of American Empire, 1767-1821; Vol. II is Andrew Jackson and the Course of American Freedom, 1822-1833; Vol. III is Andrew Jackson and the Course of American Democracy, 1833-1845.
  
  Old Hickory's War: Andrew Jackson and the Quest for Empire by David and Jeanne Heidler is also worth reading.
  
  
• Theodore Roosevelt
  
  Edmund Morris's 3-volume biography. Vol. I, The Rise of Theodore Roosevelt; Vol. II, Theodore Rex;, Vol. III, Colonel Roosevelt
  
  
• Harry Truman
  
  Man of the People: A Life of Harry S. Truman by Alonzo Hamby
  
  
• John F. Kennedy
  
  The aforementioned American Presidency Series book, The Presidency of John F. Kennedy, revised edition by James Giglio.
  
  An Unfinished Life: John F. Kennedy, 1917-1963 by Robert Dallek
  
  
• Lyndon Johnson
  
  Robert Caro's multi-volume biography (still unfinished). Vol. I, The Years of Lyndon Johnson: The Path to Power; Vol. II, Means of Ascent; Vol. III, Master of the Senate; Vol. IV, The Passage of Power; Vol. V is yet to be published.
  
  For a one volume account, LBJ: Architect of Ambition by Randall Woods is also good.
  
  
• Richard Nixon
  
  Strangely, there still isn't a definitive book on Nixon's presidency. For a good understanding of his presidency, you need to get into more specific areas, like Nixon and foreign affairs, Nixon and the civil rights movement, or even biographies of Nixon's closest advisers within his administration. The best account of Nixon himself would by the American Presidency Series's entry by Melvin Small, The Presidency of Richard Nixon. Equally important when attempting to understand Nixon's presidency is the life and thought of Henry Kissinger. The single best biography of Kissinger is Jeremi Suri's Henry Kissinger and the American Century.
  
  
• Gerald Ford
  
  Really the only substantive book on Gerald Ford comes from the American Presidency Series. It's The Presidency of Gerald R. Ford, revised ed by John Greene.
  
  
• Jimmy Carter
  
  The more substantive books on Carter are going to be too dry reading than what you're asking for. A readable, and analytically thorough, biography of Carter's presidency is The Presidency of James Earl Carter, Jr., revised and updated edition by Burton Ira Kaufman. For Carter's (much more effective) time post-presidency, check out Douglas Brinkley's The Unfinished Presidency: Jimmy Carter's Quest for Global Peace. For the Carter presidency's foreign policy, still the best account is Morality, Reason, and Power: American Diplomacy in the Carter Years by Gaddis Smith.
  
  
• Ronald Reagan
  
  It's hard to find a good, unbiased biography of Reagan. By far the best biography comes from the journalist Lou Cannon in his book, President Reagan: The Role of a Lifetime.
  
  Sean Wilentz's The Age of Reagan: A History, 1974-2008 is also good, but the author becomes more clearly biased as the history gets closer to the present. Still, despite the author's biases it is a great book that is analytically sharp and incredibly well written.
  
  Morning in America: How Ronald Reagan Invented the 1980s by Gil Troy offers a solid, more positive assessment of Reagan than most historians provide.
  
  
• George H.W. Bush
  
  The American Presidency Series's entry by John Greene, The Presidency of George Bush
  
  
• Bill Clinton
  
  Historians are just now starting to dig into the Clinton presidency. The best account of the Clinton presidency, like Reagan's presidency, comes from a journalist: John Harris's The Survior: Bill Clinton in the White House
  
  There are also a ton of books on the George W. Bush presidency, many of them good, many of them bad. While I'm not a big fan of this sub-reddit's 20 years prior rule, I will respect it. If you want some suggestions on George W. Bush, just PM me.
  
  Edit: I realized I completely left out John Quincy Adams so I added him in.
  Edit #2: I also linked my suggestions to their respective Amazon page.

Shamless plug for Robert Caro's magnificent books on LBJ's life. Best biographies I've ever read.

I haven't cracked them yet, but there are a few multi-volume biographies that get high marks (and since you say "the bigger the better..." :))

• Edmund Morris's trilogy on Teddy Roosevelt
  
• Manchester's The Last Lion series on Churchill
  
• Caro's The Years of Lyndon Johnson
  
  I also just had a friend send me Captain Sir Richard Francis Burton which seems like an interesting read.
  
  None of these are explicitly reformed, so I apologize if that's what you're looking for. But these are all acclaimed reads about men with a remarkable impact on history, which is worth attention anyway in my opinion :)

• The Gate by Francois Bizot. French anthropologist working in Cambodia at the time the Khmer Rouge came to power:
  > In 1971, on a routine outing through the Cambodian countryside, the young French ethnologist Francois Bizot is captured by the Khmer Rouge. Accused of being an agent of 'American imperialism', he is chained and imprisoned. His captor, Douch - later responsible for tens of thousands of deaths - interrogates him at length; after three months of torturous deliberation, during which his every word was weighed and his life hung in the balance, he was released. Four years later, the Khmer Rouge entered Phnom Penh. Francois Bizot became the official intermediary between the ruthless conqueror and the terrified refugees behind the gate of the French embassy: a ringside seat to one of history's most appalling genocides. Written thirty years later, Francois Bizot's memoir of his horrific experiences in the 'killing fields' of Cambodia is, in the words of John le Carre, a 'contemporary classic'.
  
  
• The Years of Lyndon Johnson by Robert Caro. Four volumes, with one more to follow. Both a brilliant biography of a fascinating character, but also a great study of a turbulent part of American history and more generally of the nature of political power.
  
  
• A Fish In The Water by Mario Vargas Llosa. Biography of great Peruvian author - alternates chapters between his growing up and becoming a novelist, his first love etc, alongside a narrative of his campaign for the presidency. His politics are quite different to mine, so I preferred the life story parts! If you like that, maybe try his novel Aunt Julia and the Scriptwriter, which is a fictionalised account of his own story.
  
  
• Emergency Sex (And Other Desperate Measures). Three friends who end up working for the UN in various conflict zones and humanitarian disasters around the world. It's a great mix of stories about their (mis)adventures alongside thought provoking stuff about peacekeeping, aid and getting involved in conflicts. Well worth a look.