I can't say this is a recommendation BUT I'm currently reading (on and off) C++ Concurrency in Action by Anthony Williams. It's certainly filling in a lot of what I don't know about multi-threading and exposing me to a few other features in the STL that I've not used before. Although I do have a multi-threaded app that I've implemented a few of the things I've learned in I don't feel that I needed to code anything at all to get use out of this book.
I'll also add that the publisher has a thing where if you buy a REAL book you also get the ebook version for free which is great. I love having a real book but I'm becoming a fan of ebooks now so good to have both.