The "Cook" guide is geared solely to tourism and hyped the more Big
Name Islands than many others.
I've often disagreed about many of it's opinions about Greek Islands
that I've gone to that it has criticized.
Tommyk5, Let's take a good long look at the Thomas Cook Island Hopping Guide (18th edition) and compare it to Bradt Guide Northern Greece (2020), my current favourite, where you really do get it all...
HOURS LATER...
Both guide books cover Thessalonica and the island of Thassos, which means that a comparison is meaningful. The Bradt guide has more extensive coverage as it is dedicated solely to Northern Greece and is, somewhat undeservedly, kinder to Greece's second city. The Cook guide describes the Thessalonica I remember, a Miami on the Mediterranean, with a shortage of Greek ruins from antiquity and no easy access beach. Thassos is described accurately, as far as I can tell, as both books seem to be describing the same island.
The Cook guide is excellent, and is one of the most comprehensive, detailed and thorough guidebooks I have ever seen, and is very accurate in it's descriptions of Poros (don't you just hate an island that isn't even really an island) and other places such as Crete. There are maps showing high season ferry routes, low season ferry routes, trunk ferry routes, domestic rail network, domestic flights, ferry routes for every island group including required travel time between the individual islands comprising that particular group, international ferry routes to/from Italy, a description and evaluation of every ferry operating in Greek waters (!), mentioning them all by name, descriptions of islands, ports and towns, a comparison of over 70 islands according to 10 criteria, and there is even an honourable mention of the island of Imbros.
Want details? This is as good as it gets!