This one was published around 2015.
336-page hard cover book that looks at every song that The Seekers have recorded.
Lots of history, trivia and memorabilia.
Still available from Amazon for around $40-$50 new (less for used) or at a considerably higher price if you want one personally autographed from The Seekers' website.
I bought one for a good friend of ours as well as an avid Trio fan a few years ago.