I love curated checkmate training, and I would disagree with the other posters. I would in fact recommend you don't make the training "random", but keep them in line with the book. Presumably, like Polgar Mates, there's a sequence to it.

The main thing I'd recommend is having illegal moves do nothing, and make drag and drop more clear. The "floating ghost piece" is actually not the cursor, and that's kinda not very nice UX. You might try a "click to place" technique instead of drag & drop.

Is this book out of copyright now?