I agree that many people like it more when chess puzzles do not give a clue on the tactical theme. That is not my question, and I would like to focus on how to study a collection of chess puzzles classified by themes. I have one of those books, with one chapter devoted to each theme. In each chapter the difficulty is supposed to increase.
When I was preparing for undergraduate math exams, I used to rotate the exercises: one exercise per chapter, instead of devoting myself to one chapter exhaustively until jumping to the next one. That way, I was reviewing all the material in each session and was exposed to a bit of everything all the time. This approach has always served me well.
So I am doing the 1st chess puzzle in each chapter and, after reaching the end of the book, I go back to the beginning and solve the 2nd problem of each chapter and so on.
However, authors do not seem to have designed chess puzzle books for this approach. Sometimes they may even give detailed instructions like "look at each puzzle for 5 minutes and then look at the solution", "try to be exposed to 20 puzzles per day in order to develop a sense of pattern recognition" but there is no mention to this rotation approach I think I should use.
Is it better to focus on one tactical motive for a while instead?