I'm interested in doing some thorough reading about the presidents, specifically both Roosevelts, Wilson, Kennedy, LBJ, and Nixon. What are the quintessential historical biographies of the presidents?
For Teddy Roosevelt, the most comprehensive and well-written biography is Edmund Morris' 3-volume series. For Wilson, I think John Milton Cooper's biography is far and away the best. For both JFK and Nixon, I still don't think anyone has written the "definitive" biography that scholars point to as the go-to source. Robert Dallek's bio of JFK, An Unfinished Life is pretty good and so his James Giglio's The Presidency of John F. Kennedy. Joan Hoff's Nixon Reconsidered is a major biography that is fairly controversial as Hoff offers one of the few positive portrayals of Nixon's presidency. Tim Weiner's One Man Against the World is a good, albeit superficial biography of Nixon. John Farrell's Nixon biography (which will be released later this month) is already making some pretty big waves and might end up being the best Nixon biography yet. There's several excellent biographies on LBJ. The most obvious is Robert Caro's 4-volume series. Unfortunately, the series is not yet complete; Caro has only gotten up to LBJ's ascension to the presidency after JFK's assassination. The final volume will be published some time in the indefinite future. If you don't want to read over 3000 pages then there are several other good biographies of LBJ, like Randall Woods' Architect of Ambition. Robert Dallek also has a 2-volume biography of LBJ that is also very good.
Theodore Rex is a very complete bio of T.R.'s Presidency. About 700 page, very thorough if you want a really in depth look into it. There's a trilogy too, on what his life before POTUS and a book for after too.
David McCullough does an excellent job on Harry Truman and John Adams too. Very well respected author in the academy and very respected biographies.
Nixon gets a tough beat for Watergate. As a POTUS, he was a remarkable POTUS, but watergate and the shadiness overshadow all his achievements (he created the EPA, opened trade with China, instituted Affirmative Action, laxed tensions with Russia, got SALT signed, eventually got us out of Vietnam), almost signed single payer healthcare but ah Ted Kennedy pushed him too far.