The reason why you might choose the latest guide book is that the accommodation details are likely to be the most up to date. Not very much else will have changed otherwise from one year to the next. If you use an app it will be updated more frequently and will always be the latest version. Personally I like a paper guide book, particularly for planning, including planning the days ahead as I walk. I use the Village to Village guide and like the profile overview of the whole Camino inside the front cover. I also use the Wise Pilgrim app. Plus I look at Gronze online which has up to date accommodation details.
I set off for the
Camino Frances in 2 weeks time. I can tell you more about August-September once I've finished
However weather conditions are far less predictable than they used to be! I am prepared/expecting hot weather first with rain possible later.