I'd recommend the book to anyone, even if only for its historical value as one of the lasting early[1] self-help books (together with Napoleon Hill's, I guess). There are some good insights in the book that are worth following.
However, it shares some of the problems that many modern self-help books have as well: very high on anecdote and broad generalizations, yet very light on evidence, or even considering alternative explanations for observations.
[1] Of course, self-help books are as least as old as Marcus Aurelius' Meditations...
In the very back of Kaj's excellent How to Run a Successful Less Wrong Meetup Group booklet, he has a recommended reading section, including the classic book How to Win Friends and Influence People.
It just so happens that not only have I read the book myself, but I have written up a concise summary of the core advice here. Kaj suggested that I post this on the discussion section because others might find it useful, so here you go!
I suspect that more people are willing to read a summary of a book from the 1930s than an actual book from the 1930s. What I will say about reading the long-form text is that it can be more useful for internalizing these concepts and giving examples of them. It is far too easy to abstractly know what you need to do, much harder to actually take action on those beliefs...