If it's just a book about apostasy and how it affects small religious groups like the JWs, I doubt anyone will care much. That is just more of the usual WTS propaganda. If it is an attempt to engage with anti-JW or anti-WTS claims or accusations, it could end up working against the WTS. The last thing they want is JWs hearing those arguments, since it could lead them to search for more info outside of the organization, and that could lead them right out of the organization.
Either way, I doubt the GB is happy about it. They consider themselves the only legitimate conduit for information and teaching, and they really do not like it when anyone (especially a JW) tries to 'add any spiritual food' to the JW table. If they let this guy do it, then any JW can write a book to "help" other JWs out. If anyone is likely to stop this guy from ever publishing again, it's the WTS. How long before a trio of elders visits him to 'provide necessary guidance' and save his eternal soul?