What recommends Joshi's biography "H.P. Lovecraft: A Life" in the first place?
Besides being full of details from Lovecraft's life?
The book has received some hard criticism. As I understand it, Joshi has difficulty holding an objective perspective, adding his own very personal opinions, and moralizing over Lovecraft. And lacking respect towards Lovecraft's person, in telling of private and personal things in a detached and degrading way that a friend never would have done, and which certainly would have offended Lovecraft had he been alive (compare this to the way Dr. Farmer tells of Smith's life; even if he reveals some weakness of Smith's, it is still told from a perspective of genuine respect and integrity).
For example, the review "Difficult mixed bag - comprehensive but needs editing" at Amazon.
http://www.amazon.com/H-P-Lovecraft-S-T-Joshi/dp/0940884887/ref=sr_1_1?ie=UTF8&s=books&qid=1252079007&sr=1-1
This certainly repels me. For the time being, for biographical details, I am content with reading Lovecraft's own letters and the book "Lovecraft Remembered".