How important is it to learn DNN/NN from scratch? I have several years of experience working in the tech industry and I am learning DNN for applying it in my do

How important is it to learn DNN/NN from scratch? I have several years of experience working in the tech industry and I am learning DNN for applying it in my domain. Also for hobby side projects. I did the ML Coursera course by Andrew Ng a few years ago. I liked the material but I felt the course focused a little too much on the details and not enough on actual application. Would learning DNN from a book like 1. https://www.manning.com/books/deep-learning-with-pytorch https://www.manning.com/books/deep-learning-with-pytorch or 2. https://www.manning.com/books/deep-learning-with-python-second-edition?query=deep%20learning%20with%20python https://www.manning.com/books/deep-learning-with-python-seco... Be a better approach for someone looking to learn concepts and application rather than the detailed mathematics behind it? If yes, which of these two books (or alternative) would you recommend ?