@drinkswriter@writingcommunity@writers Asking questions - and raising points - that you reveal in the book is the traditional way to approach newsletters pre-release, though normally there's a fair bit of time, and you can build anticipation. If the date is drawing nearer, then a more direct, blunt approach might be called for.
The best research is actually reading a lot of these types of newsletters in preparation for this, then finding your own take on common formats.