I am currently reading it, it is very nicely written and accessible. Each chapter starts off gently so you can skip to the next whenever you feel lost, only to

I am currently reading it, it is very nicely written and accessible. Each chapter starts off gently so you can skip to the next whenever you feel lost, only to come back later. So far: introduction/preorders, monoidal preorders/wiring diagrams, categories/application to database schemas. For those reading on a ebook, the book sources are available on its arxiv page https://arxiv.org/abs/1803.05316 https://arxiv.org/abs/1803.05316 so you can build a custom pdf for your device.