That book is great if you want to go in-depth! If you're a practitioner who wants to get to a trained model as quickly as possible, you're probably better of just following a tutorial. The official Keras tutorial on segmentation looks pretty good [1]. We also have a blog post with code samples on how to set up an image segmentation workflow with Segments.ai and Facebook's detectron2 framework [2].
[1] https://keras.io/examples/vision/oxford_pets_image_segmentat...
[2] https://segments.ai/blog/speed-up-image-segmentation-with-mo...