Unequal

The Maths of When Things Do and Don't Add Up

By: Eugenia Cheng

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Hardcover | 2 September 2025

At a Glance

Hardcover
400 Pages

Dimensions(cm)
22.0 x 13.8 x 3.7

Hardcover

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From Uniqueness to Set Theory and beyond, climb the mathematical ladder of sameness and difference with award-winning mathematician Eugenia Cheng

At first glance, the concept of equality in maths seems unambiguous. Denoted by two parallel lines, the equals sign looks elegant, simple and entirely black and white.

But between those two lines lies a grey area, a world of flexibility, creativity and innovation. And once you see this nuance, you quickly realise that sameness and difference, equality and inequality, are not nearly as immutable as they may seem. In fact, they are the opposite: a mathematical playground of choice and abstraction, leading to far greater insight than you could have dreamed.

In Unequal, Mathematician Eugenia Cheng explores the rich and rewarding world of the interplay between sameness and difference, from numbers to manifolds to category theory and beyond.

About the Author

Eugenia Cheng is Scientist in Residence at the School of the Art Institute of Chicago and Honorary Visiting Fellow of Pure Mathematics at City, University of London. A Cambridge graduate, she previously taught at the Universities of Cambridge, Chicago and Nice. She is also a concert pianist, fluent in French, and the author of several Profile bestsellers, including How to Bake Pi and x + y. In 2017 her book Beyond Infinity was shortlisted for the Royal Society Science Book Prize.

Industry Reviews

"PRAISE FOR IS MATHS REAL?

'A generous tour of mathematics for anyone whose instincts tend less towards ""Just tell me the answer"" and more towards ""Wait, but why?""' - Jordan Ellenberg, author of 'Shape'

'Intriguing ... Celebrates the dizziness and disorientation engendered by childlike questions that hint at the deep mysteries beneath' - Anil Ananthaswamy

'Passionate, eye-opening and accessible ... a love letter to the curious spirit of the discipline' - Waterstones Best Books of 2023

'A brilliant rebuttal to those who see math as only about right answers, rather than about creative discovery. [Cheng] masterfully uncovers what's simply profound in the profoundly simple' - Francis Su, author of 'Mathematics for Human Flourishing'"

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