Depends which type of Morrison bio you wanna read.......I'd say, overall Jim Morrison by Stephan Davis would be the best.......Light my Fire my Ray Manzarek is good too, but I'm pretty sure Ray has a man-crush on Jim. Riders on the Storm by Densmore was good, but he seems a little bitter towards Jim. Wild Child my Life with and Without Jim Morrison by Patrica Kenealy-Morrison was pretty crappy, she's the one who Morrison married in the Wiccan ceremony. I read somewhere she's not sure if her whole experience with Jim actually happened or was the product of copious drug intake (it may have been the Davis book that stated this). The Lizard King by Jerry Hopkins is pretty good, basically a rehash of NHGOA, but with some ammendmants. The book has been in print for 20 years or so now and still does not see fit to correct several mistakes with dates in the text (such as a description of what Morrison did in 1987, some 16 years after he was dead).
I've read a lot of Morrison bios and 95% of it is the same information. If you can get ahold of them, read them all and form your own opinion, if not, check out the one by Stephan Davis, it's the most in-depth one (though the first to suggest Morrison had homosexual tendancies)
The problem is ALL the Doors biographies are erroneous to an extent.
It's hard because the band is a myth at this point in time; there are so many mysteries and enigmas involved with that band. Krieger and co. never clarify anything and sometimes they contradict themselves, too (stuff Krieger said happened he later admitted never happened; they imply Morrison is still alive at times and at other times laugh off the idea; they're just doing it to keep the memory alive and promote their new band, Doors of the 20th Century).
Stephen Davis' book isn't any better than Sugerman's, in fact Sugerman's is better. The only thing I find interesting about Davis' is that he claimed Morrison experimented sexually with other men; I can totally believe this given Morrison's sexual liberty, his outlook on life, his actions and things he said and just the general nature of the man; plus, he was around when anything went basically.