Clothes may not make the man, but they can certainly be his undoing.

As Shakespeare noted way back in 1601, speaking through Polonius in "Hamlet": "Costly thy habit as thy purse can buy, But not express'd in fancy; rich, not gaudy; For the apparel oft proclaims the man."

Generally speaking, that's true. Clothes matter because they serve as a visual shorthand, sending out signals we are all practiced at reading. Before a word is said or knowledge of any kind is exchanged, we have determined who a person is based on his or her apparel. That doesn't necessarily mean we are right -- how many people thought scraggly old Howard Hughes was a bum? But more often than not, we are.

"Nordstrom Guide to Men's Style," Tom Julian's wonderfully practical new handbook, is a must for every man. Of course, those who need it the most are the least likely to peruse its pages. But Mr. Julian, a consumer trend expert and former fashion director for the Men's Fashion Association, has compiled an invaluable source of information based on his 20 years in the business.

"The men's fashion industry is over $50 billion a year, driven now more by sportswear and accessories and unexpected categories like denim," he says. "When I started in the '80s it was about labels and manufactured suits, shirts and pants. Today we've seen this embrace for different ways of dressing that includes everything from work to travel, from region to physique."

Mr. Julian, a native of Clairton, launched the Tom Mr. Julian Group last year after working for advertising agencies Fallon Worldwide and McCann Erickson. His expertise has been utilized by media outlets such as CNN, and his clients have included Nike, BMW, Starbucks and Coke. The "Men's Style" book was an idea Mr. Julian had when he started talking with Nordstrom, with whom he had a 10-year relationship, about working with his brand consultancy company.

"The Nordstrom customer was kept in mind from start to finish, but the book is about real men who shop in all channels and still end up having the same problems. How can I be better educated, how can I be more confident in what I wear, and how can I build the right closet for my lifestyle?"

Step by step, Mr. Julian lays out the four types of men's style and helps readers identify which is theirs: luxury (think George Clooney), classic (Matt Damon), contemporary (David Beckham) or trend (Justin Timberlake). The book tackles every component of a well-dressed wardrobe, with chapters on suits, sport coats, trousers, shirts, neckwear and tuxedos and has a terrific resources section. This includes "Ask the Nordstrom Tailor," how to iron a shirt, pack a suitcase, remove a stain, organize a closet, and clothing care with a guide to universal symbols.

"I think American men have become very aware of style and what it does for them in their work life and personal life. To a degree there's also an understanding that fashion can have a little bit of fun attached to it," Mr. Julian says. "One guy is never going to be 100 percent one type -- we mix them in the book, show how to wear a blazer four ways, how to take a fall suit and make it right for a weekend outing."

Several decades ago, 80 percent of men's clothing was bought for them by women. Today it's 60 percent. Some studies show that men buy more online than women, depending on the site, because it's time-saving, convenient and very analytical.

"Men's fashion has changed faster in the last 20 years than in the last 40. That's because of lifestyle. Decade by decade there were such iconic movements. Nothing is as sweeping today. That's why we can't put rules out there. Our cover is the best example -- it shows a variety of men in a variety of lifestyles, from tailored to sportswear," Mr. Julian says.

The advent of casual Fridays in the '90s and the metrosexual look this decade have been among the catalysts for change in the menswear industry. Mr. Julian notes that shopping for men used to be easy -- a basic navy wool suit in a year-round weight pretty much covered the territory.

"A lot of guys will say, 'I get how to buy a car, I get how to buy electronics. Because I have information available to me I feel smart. But when it comes to clothes I don't feel as smart,' " says Mr. Julian. Now they can.

"Nordstrom Guide to Men's Style," with a foreword by Pete Nordstrom, is available for $19.95 at the store in Ross Park Mall, at Nordstrom.com. and Amazon.com and at book stores.