I've read a number of Jon Ronson books covering some interesting encounters with Mr Icke.
TBH I didn't realise he was still alive.
IIRC, he gets some coverage in "The Psychopath Test: A Journey Through the Madness Industry" and "Out of the Ordinary: True Tales of Everyday Craziness" and/or possibly "Them: Adventures with Extremists".
The titles alone may give a flavour.