I'm not sure what to make of this Taraborelli either. I haven't read the latest version of this book but read two earlier versions. The first one was by far the best. It came out around 1990/91 and was fascinating, really detailed and seemingly well-researched with some pretty hair-raising revelations about the Jackson family and on the whole was very sympathetic and fair to Michael.
So i thought he was quite reliable and was interested to read the updated version when it came out while Michael was awaiting trial. I was really disappointed. First of all, i thought it would've been better if he'd just written a totally new book, starting from where he'd left off with the first one, as he'd re-written/cut out lots of detail from certain events so it wasn't as good. Plus, he'd changed the wording of some conversations that were in the first book which made me wonder if they'd happened at all.
In the 'new' sections of the book he seemed much more 'tabloidy' and judgemental than he had been before, and just wrote some stuff which didn't ring true for me. Also, he wrote about conversations that supposedly happened when there was no-one else in the room but Michael and the person he's talking to (eg. Liz Taylor, who i seriously doubt would be telling JRT what they'd been talking about) and even sometimes things that happened when only Michael was there. How would he know?
On the other hand I have seen him interviewed and he does seem to actually like Michael, and I think he's still probably more reliable and fairer than a lot of other biographers out there. Maybe his publishers put pressure on him to be more scandalous and anti-michael after there were allegations made against him.I know Aphrodite Jones was told she couldn't publish anything pro-jackson (!). I do think he's the most reliable biographer there is, but let's face it that's not really saying much.