...by Catherine Clinton is one book I'm currently enjoy reading - a quite "entertaining" outline with some points, aspects and angles that were new to me. I'd probably less suggest it to a "beginner" with zero "basic" knowledge on Mary Lincoln and her life (as I wouldn't have gotten certain references/statements/etc. then), nor to someone looking for the one-and-only universal bio. This is, of course, my very personal opinion and preference, others might sure disagree. However, I'd recommend it to anyone interested in "more" on Mary Lincoln from a further point of view.
http://www.amazon.com/gp/aw/d/0060760419...ot_redir=1