Glancing at the reviews for this book, I noticed that they are remarkably polarised - either '5 stars, it changed my life' or '1 star, borderline heresy'. I read the book a few years ago and then as now I can sympathise somewhat with both extremes.
The negative reviewers seem to have approached the book expecting to find fault with it, and indeed there are faults to be found. Eldredge's Biblical exposition is often simplistic and selective. Also, he's clearly a very outdoors-y kind of man, and most of his specific examples about manliness seem to reflect that.
Nevertheless, although I'm very different from the author in temperament and interests, I found that a lot of his insights about the nature of manliness really ring true. His summary that deep down men want a battle to fight, an adventure to go on, and a beauty to win hits the spot as far as I'm concerned. Of course all of these can be directed in a worldly direction and some of Eldredge's examples seem to do so.
But if the battle is against sin, the world and the devil, and the adventure is discovering and carrying out God's will in your life, these can be biblical, Godly desires. In my own case God has used these desires to lead me to live and witness for him overseas. And as for the desire for beauty, it drives me to try to cherish my wife and enrich our marriage as much as possible.
The reason this book has made such an impact is that it scratches where many men are itching and is honest about the problem the western church has with the role of men. I don't think all it's answers are correct, but when it was written there simply weren't any books covering the same ground. I look forward to reading some that provide more biblical reflection on these issues, but in the meantime this is worth reading if only to get you thinking.
In summary: is some of Eldredge's use of the Bible flawed? Certainly. But does he have valid insights into men's needs and identity? Undoubtedly. As with any Christian book you should read this critically with the Bible alongside, but if you do you'll benefit from it.