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They are short but great books. All are zipped into a single RAR file. All these PDFs have standard eBook features like OCR, bookmarks, covers, uniform page size & TOC with internal links. Few OCRing errors that have escaped me are regretted!
Here is the list: 01. Classic Brainteasers - Martin Gardener (1.55mb, 96pages) 02. Exploring Science - Martin Gardener (1.79mb, 71pages) 03. Fantastic Book of Math Puzzles - Margaret C. Edmiston (1.25mb, 96pages) 04. How To Meditate - John Novak (2.06mb, 111pages) 05. Math Amusements - Raymond Bloom (1.02mb, 96pages) 06. Searching Science - Martin Gardener (1.78mb, 81pages) 07. Superkid Science Quiz - Dilip M. Salwi (747kb, 87pages) 08. Surprising Science Puzzles - Erwin Brecher (2.08mb, 96pages) 09. Test Your Math IQ - Steve Ryan (2.13mb, 96pages) 10. Word Fun - Otto De Costa (691kb, 77pages)