Hello mojomark, My name is Alex Becker, and I am the author of the "Kalman Filter from the Ground Up book." First, I would like to thank you for your feedback. As an author, it is important for me to receive feedback from the readers. In the book's second edition, I made many changes based on the feedback from the book readers. I've elaborated explanations of the topics some readers failed to understand and added several appendixes. You are right, book authors don't get paid to respond. However, the KalmanFilter.Net is a project, not just a book. I've worked on the project for 6 years, and you will see more in the future. The goal of this project is to help people to understand and implement the Kalman Filter. The website includes a contact page: https://www.kalmanfilter.net/contact.aspx, and the book purchasers receive my email. I do my best to answer emails and help my readers if they fail to understand specific points. Regarding the issues that you and other responders raised. Scientists use terminology that looks weird to non-scientists. But I can't write an engineering book without addressing scientific terms. I agree that "Random Variable" sounds unintuitive, but this is the term. Almost any physical quantity is a random variable. For example, the temperature of your body is a random variable. You can measure the temperature using a thermometer, but it doesn't mean that its reading is your actual temperature. Your temperature is a random variable that can be described by two parameters – the thermometer reading and the thermometer precision. Understanding the "Random Variables" concept is essential for understanding the Kalman Filter. If you make multiple measurements, the temperature is described by mean and variance. You can read again the https://www.kalmanfilter.net/background.html page, where this concept is explained. Mathematicians call the mean and the variance – statistical moments. "Moments" also sounds weird. I mention this term in the introduction, but I don't use it again in the book. If the term "moments" causes confusion, I can consider removing it from the introduction. Regarding the Linear Algebra. You don't need any prior Linear Algebra knowledge to understand the concept of the Kalman Filter and implement the Kalman Filter in one dimension. However, if you want to tackle the multi-dimensional Kalman Filter, you need some basic Linear Algebra knowledge, at least matrix multiplication. Thanks again for your post, Alex Becker.