Jamie Thom summarizes many well-known works in Slow Teaching, but does not add a lot, if anything, himself. The 'slow' gets lost in the, for me, well-known concepts of modelling, spaced learning, assertive teaching, clean classrooms, peer feedback, and Sinek's leadership advice.
I hoped to find some insight into bringing more 'slow' in my day-to-day teachings, but all I got was a summary of my education bookshelf.
Also, for new teachers I would advice Thom's sources to read instead of Slow Teaching: Making every English lesson count, make it stick, the hidden lives of learners, making good progress, teaching like a champion, start with why, and why don't students like school?
I know reading all these works will go slower than reading Jamie Thom's book, but it will be more rewarding for your teaching and will prevent anxiety and stress better.