This is the hint.
This book of 60 Times2 Jumbo crosswords is the 16th such to be published by HarperCollins and contains puzzles originally published in The Times puzzle pages between March 2018 and March 2019.
Having now compiled these puzzles for many years I can say confidently that if you have enjoyed previous books in this series then you will find this one presents a challenge of an entirely similar level of difficulty. Although by its nature a Jumbo puzzle will include a wider range of vocabulary than the small daily puzzles, the intention remains the same: to give a gentle workout to the mind, perhaps spurring it to recall half-forgotten references when a few letters appear in the grid or maybe to reintroduce a solver to the occasional tnteresting word they may have lurking, all but forgotten, at the back of their mind.
One such item, 34 Across in Puzzle 40 in this collection, caused one solver to write in, claiming it was certainly not a word. I was able to point out that is was in both Collins English Dictionary (the recommended dictionary for the Times2 crossword) and Chambers Dictionary and therefore perfectly fair game for an occasional appearance in the puzzle. In my reply I was able to observe the pleasing fact that the word was clearly unusual in being entirely self-referential by defining its own characteristic nature. I can’t help thinking the language would be far poorer if it did not include words only rarely appearing in general use with which crossword setters may sometimes bamboozle and tease their solvers!
I don’t often hide things in the Jumbo puzzle grids in the same way as I do with the daily Times2 puzzles but one personal landmark I thought worth commemorating was reached with the puzzle numbered 55 in this collection. This was the 1000th Jumbo crossword I had compiled for The Times (counting those in both the Times2 (827) and cryptic (173) series at that time) and the occasion is marked in the particular choice of words with which the grid is filled, a self-imposed constraint that made construction of the grid a little trickier than usual, though the result could be no more difficult than normal for the solver.
Once again I must thank my fellow Times setter Roger Phillips for his meticulous proofreading of this book.
And with that, it only remains for me to wish you, as ever, good solving!