Lewis Carroll 
A Tangled Tale [EPUB ebook] 

Lewis Carroll (1832–1898) made his name with his Alice books in the 1860s, but also wrote on popular mathematics – he was a maths tutor in various capacities at Christ Church College, Oxford, from his undergraduate days until his death.
First published in 1885, ‘A Tangled Tale’ is a collection of ten brief humorous puzzles – called ‘knots’ – originally published in a monthly magazine in the early 1880s. Each puzzle is described in story form, then summarised as a ‘maths problem’. For the book, Carroll assessed answers sent in by readers, referring to them by name (usually pseudonyms) and grading them, with comments in typically polite-but-cutting Oxford-don fashion.