Carol Shields' is a good, short, introductory bio. Very broad, and not a whole lot of detail, but a good place for someone who's never read a bio to start, imo.

I liked Claire Tomilin's very much, though she is subject to some flights of fancy and speculation. ;-) But hers was the first in-depth bio in which I was able to keep the cast of thousands straight. There are so many neighbors and extended family members mentioned in the bios, that it's easy to get lost. I wasn't lost with the Tomalin.