A very useful tool for how to get started with a level design. It covers a lot of useful planning techniques for before you've even opened up your engine or tools; some of which I was already using but others have been a big help for the design I'm working with at the moment. I've worked through about half of the steps with this design after reading through the book and visualising the level and mapping it out has been a much easier process than usual following through some of the new techniques in here.
A great feature of this book is that it doesn't try to give you one-size-fits-all advice; it acknowledges the differences between the various kinds of environments you can design, like singleplayer levels and multiplayer maps, and alters parts of its process to accommodate for those. There's also lists of references at the back to use as inspiration, containing things like ideas for settings and a collection of different architectural styles you could use for buildings in your levels.
I did notice a few typos and mistakes while reading through, but nothing major. I also would have liked a little bit of detail (be it a sentence or two or an image) for some of the more obscure references in the lists at the end, like in the architecture and art style ones. They don't really work as inspiration if I don't know what they are so I have to use other sources to first research them in order to decide if they're useful. But these are only minor complaints, it's a really useful guide for level design.