Good news, you no longer need to remortgage the house in order to acquire a copy of David Barrett's study Fragmentation of a Sect: Schism in the Worldwide Church of God. Oxford University press is releasing a paperback edition (with a few very minor revisions) later this year.
This is an academic work focused on the sociology rather than the usual agenda-driven stuff that tends to be published elsewhere. If you prefer debunking and steamy apologetics larded with Bible texts, this probably isn't the book for you. In my view, however, the story of the dissolution of the WCG is better told without the invective. It's a story that speaks for itself, and David Barrett is one of the keenest observers of the COG phenomenon. If it helps, I'm told Joe Tkach hated it - which in my view is the ultimate recommendation.
You're going to have to wait till August to get your hands on a copy, but preorders are being taken with a price tag of $29.95 US/£19.99 UK. If that sounds expensive, be ye aware that the nice people at OUP in NZ have the locally sourced hardback edition listed at just under eighty smackers, so quit with the complaining. Amazon currently has the HB at $61.
An ebook edition you ask? Sadly not the Oxford way.
More on this closer to August.