Congrats! I never counted my sales for different periods of time, because I always felt the feedback is what counts the most to have a long tail of sales. If the feedback is positive, the sales will go on. So I rather focused on this aspect, but it seems to go well for you from the feedback side as well :)

I too released my first self-published book The Road to React on HN (initial in wrong English "The Road to learn React" haha) a few years ago and the community helped tremendously to get this project off the ground. Thanks to all of you! And I wish your success continues too :)