Definitely showing its age; the first third of the book exclusively discusses vi (not vim), to the extent that a lot of it becomes superceded by the rest of the book. The author has a serious hard-on for `troff`, one in three examples of how to do things with vi(m) is "how to format for troff", which doesn't help the relevancy issue.
Because I was reading on an ebook, the other egregious problem was a huge chunk of the book devoted to vile, kyle, elvis, and other weird vi-clones, none of which really seem to exist anymore. It's really hard to skim on an ebook, which is why I mention this.
BUT after you've got past all my nitpicking, the book is pretty good. If you're already an advanced vim-user, you probably won't get much out of it, but it's worth a skim to see if you're missing any fundamentals. I'd highly suggest the chapter on ex-commands, even if you don't look at the rest of book; I finished the book this morning and have already found a use for them.
I wanted to recommend this book, but honestly you'd probably do better just searching for vim blog posts.