Alpha Books was formed in 1991 as a computer book imprint. In 1993 it introduced the successful Complete Idiot's Guide® series, which quickly branched out into other categories. Alpha became part of Macmillan General Reference in 1995, and was retained by Pearson Education when Macmillan General Reference was sold in 1999. The imprint joined Penguin Group (USA) in 2003.
Today, Alpha publishes Complete Idiot's Guides in 30 categories and has sold over 20 million copies in 26 languages. Top selling titles include The Complete Idiot's Guide to Learning Spanish 4th Edition, The Complete Idiot's Guide to Understanding Catholicism 3rd Edition, The Complete Idiot's Guide to Music Theory 2nd Edition, and The Complete Idiot's Guide to Buying and Selling a Home 5th Edition.