Jefferson biographies come in every conceivable flavor. If you have a very large appetite, the place to start is Dumas Malone’s six-volume biography. It used to be that Merrill Peterson’s lengthy one-volume treatment won pride of place after Malone’s work, but I find it exceedingly dull — quite a difficult attribute to impart to a study of Thomas Jefferson.
For Jefferson’s presidency, read McDonald’s acerbic take. For a popular approach to Jefferson, there’s Ellis. For the Sally Hemings saga, try Gordon-Reed’s first book. Mayer is excellent on Jefferson and constitutional thought — state and federal. For Jeffersonian political economy, I recommend McCoy’s _The Elusive Republic_. Jeffersonian foreign policy is the subject of the Onufs’ _Federal Union, Modern World_, which I quite like.
A fine book of essays on various questions Jeffersonian is Peter Onuf, ed., _Jeffersonian Legacies_. There you’ll find outstanding chapters on Jefferson and slavery, Jefferson and religion, Jefferson and foreign policy, etc. Still the place to start for Jefferson’s presidency is Henry Adams’s multi-volume book (available in one volume from the Library of America). Adams was a fine prose stylist with an engaged, critical approach (he was John Adams’s great-grandson).
I’m currently working on a volume about the Jefferson-Hamilton rivalry, which will be published in 2014 (if the Good Lord is willing and the creek don’t rise). If you have questions about books covering Jefferson and other topics, just ask. I would note that David Barton’s book on TJ, like most of his oeuvre, is tendentious and unreliable: he starts from his conclusions and then tries to prove them, often by miscasting evidence. Avoid.