The Affordable Baby. By Darcie Bundy. Harper & Row. $6.95.

"The Affordable Baby" is subtitled "A Complete Consumer Guide to Costs & Comparisons for Parents-to-Be" -- and that's exactly what this fact-filled volume is. Darcie Bundy, an economics writer and consumer expert, describes what expenses you should expect once you decide to have a child, and how to evaluate the cost of services in light of your own special needs and budget. By planning ahead, knowing what the baby-related expenses are, informing yourself of your options and learning how to pace your baby-related purchases, you can avoid the unexpected and plan effectively against overspending.

Described in detail is everything you need to know about medical care and costs: health insurance, obstetrical care, the less routine medical tests and expenses of pregnancy, hospital care, the alternative birth centers, pediatric care and health maintenance organizations.

"The Affordable Baby" is a comprehensive, practical and specific consumer guide to all the goods and services that parents-to-be and new parents need and want. It explains why and when you need them, how to select the best versions of them, what they usually cost and, if possible, how to limit that cost.

It is the author's opinion that everyone can afford a baby -- it's just a question of how well you anticipate and manage the expenses. Knowing what expenses lie ahead, understanding your options, avoiding financial surprises and pitfalls and planning ahead all will smooth your financial transition to parenthood.

"Affordable Baby" also deals with the dilemma of whether mothers should return to work or stay home with the baby.

In the Childcare section, Bundy offers tips for finding and keeping good in-home care. After all, home is the most convenient setting for a baby's care -- no lugging the baby and equipment around town to a sitter or day care center.

Other useful information deals with why new parents should have a will drawn up; how to shop for life insurance policies; how to recognize good value in maternity and baby clothing; how to select a good, safe highchair, crib and walker; how to save for your child's education; and how to check your health insurance policy to make sure you're covered for whatever expenses lie ahead. Peak Condition. By Scott Madsen. Simon & Schuster Inc., $9.95.

Scott Madsen may not be a familiar name, but his lean, muscular body shown in the Soloflex ad has earned him fame in the exercise world. In his book "Peak Condition," Madsen shares the methods he ostensibly used to reach peak condition.

Before even finishing the introduction, however, it becomes evident that Madsen's publication is more of a sexy photo album than a book about physical fitness. It is also evident that Madsen's idea of "peak condition" certainly isn't the "peak condition" most athletes hope to attain: "Being a good influence on yourself," he says in the first line of the book, is "what being in peak condition is all about!"

That's one factor en route to peak condition, but this alone didn't make Madsen the competitive gymnast he was at Berkeley. Neither did the workouts in this book.

"Give yourself half an hour three times a week, pick a program that suits your frame of mind for that day, and then do it," he recommends at the conclusion of the introduction. "Being in peak condition will allow you to give that peak performance . . ."

If that's how Madsen trained to be a competitive athlete, please sign me up immediately.

Most of the 160-page book is flooded with pictures of Madsen, and what little discussion there is about physical fitness is vague and trivial. After a very fine chapter on warming up and cooling down, Madsen demonstrates the use of free weights. He never says why you should use free weights or how much weight one should lift, just that you should "Start with the minimum numbers of repetitions and sets and take at least three to four weeks to increase to the maximum numbers."

Madsen says he's "not very impressed with the exercise-machine infatuation," then takes 15 pages to show himself working on these machines. What follows is a chapter on calisthenics -- push-ups, sit-ups and jumping jacks -- of which Madsen says can "certainly fill the bill" in attaining physical fitness.

Again, in his brief description of aerobic exercise, Madsen fails to explain why people should exercise aerobically. "Aerobic exercise is this year's better mousetrap," Madsen writes. "It seems that swimming, brisk walking, jogging, falling in love and other forms of exercise that make your heart beat faster have been replaced by a program of dynamic body movements performed at a steady pace, or 'aerobics.' "

Too bad that another celebrity has chosen the physical fitness market to peddle his name and body with a book that does little more than show off a physique that obviously was not developed by following his own book's advice.