While viewing a CSPAN2 Booktv program last year(I wish I could remember which one), a historian mentioned that Michael Burlingame was working on a multivolume biography of Lincoln. Unfortunately, since that time I haven't seen any further mention of such a project.
Michael Burlingame's The Inner World of Abraham Lincoln (University of Illinois Press, 1994) is my favorite 'Lincoln book'. It's been called a psycho-biography. This is unfortunate in some ways because the book isn't a biography in the classic sense and so many previous authors, perhaps in an attempt to make their mark in a crowded field, have vastly overreached when constructing their conclusions from the available evidence. Right or wrong, the psycho- prefix has reflexively become a bit of a pejorative term in the minds of many readers. In my opinion, Michael Burlingame's work in this regard is among the best out there. His measured approach takes neither criticism nor praise too far and he generally avoids the overreaching conclusions mentioned above that harm the credibility of so many writers (at least that's my memory of it).
Inner World is a collection of excellent essays dealing in turn with AL's ambition, anger, and depression; along with his attitude toward marriage, women, parenting and slavery. My personal favorite is the very first chapter, which traces Lincoln's development from party hack to statesman. Burlingame marks the transformation in the context of a midlife crisis of sorts. I was immediately hooked as this aspect of Lincoln's political development was something I had never seen in any other scholarship--although admittedly I don't read the majority of the new Lincoln stuff that spews forth every year. On the other hand, in Inner World, some important issues were left out. One notable omission was a self-contained essay on Lincoln and religion/spirituality.
Frequent scans through the upcoming and new release CW books on Amazon seems to reveal a marked uptick in Abe Lincoln 'issue books' over the past year or so. I hope readers don't confuse The Inner World of Abraham Lincoln with Tripp's The Intimate World of Abraham Lincoln.