I have read A LOT of watercolor books over the years, and I find Hazel Soan's content to be among my favorites. This appears to be a bit of a mix of already published content from other books, with some new stuff. I read the initial copy from my library and wanted to grab a copy for myself, which was a bit spendy because it's a UK-only printing.  Anyway, a great overview of watercolor techniques for advanced beginner to intermediate painters, with some great ideas and examples for more advanced folks too.