Millionaire baseball card dealer and maven Rosen earned the sobriquet ``Mr. Mint'' for his reputation for paying ``a mint'' for ``mint'' or top-grade cards. Despite being known as brash and outspoken, his book is full of well-tempered advice. He stresses the importance of card condition, and adds that every investor should start off as a collector so as to know the field. He talks about other baseball collect ibles, including autographed balls and bats, pins, pennants, and more. Altogether, his guide is an entertaining book that adults and savvy teens--collectors and investors alike--will enjoy. Libraries should also consider Paul M. Green and Donn Pearlman's Making Money with Baseball Cards (Bonus Bks., 1989), which provides more background on the history of cards; and Green and Kit Kiefer's Top 100: The Best Baseball Cards To Own (Bonus Bks., 1990), which subjectively rates and discusses the top 100 buys. Along with a standard price guide or two, these books will help fill out any collection on the multimillion dollar industry of baseball collect ibles.-- Paul Kaplan, Dakota Cty. Lib., Eagan, Minn.