The author has written a bunch of books about math (like The Complete Idiot's Guide to Precalculus, The Complete Idiot's Guide to Calculus (Second Edition), and The Humongous Book of Calculus Problems).
His website, www.calculus-help.com, hosts over a thousand unique visitors a day, even though it features an unflattering animated graphic of him dancing at his wedding.
(from the back of one of his books)
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