Criado Perez has assembled a vast array of data here, from a variety of fields. Her contention is that because researchers - and designers, practitioners and others - use male bodies, behaviours and lifestyles as the default, much of the world is poorly designed for women. This applies to everything from public transport routes designed primarily for 9-5 commuting through to heart disease medication that doesn't work on women.
The book is at its most powerful when she articulates the ways in which studies - especially medical studies - have generalised based on all-male samples over and over again (crash test dummies was another gotcha).
But ultimately I did have some issues with the book. It is much less convincing in arguing that all studies must have gender disaggregation to ensure women's needs are met. There is a slightly sticky point here that women are more than 50% of the population, so any study truly representative of the population shouldn't be biased against women by default. They often are, of course, but this can't be explained just by data gaps, but rather by systemic social factors. Which would bring me to my real problem here - the lack of any structural critique of sexism as a power structure. There is scant discussion about how race, class or wealth intersect, a deficit which Criado Perez admits, but accredits to the paucity of data disaggregated into BIPOC women, for example. But it is part of an approach which doesn't look at how research is shaped by broader social structures - in the end, this is a bit of a "sexism happens because men are sexist" view. 
Without that, this often feels like a huge dump of data, one curated to shape the argument of the author. I'm not challenging that her basic premises are correct, but it didn't have the thoughtfulness I tend to like in my non-fiction.