Manfredo Perdigão do Carmo (15 August 1928, Maceió – 30 April 2018, Rio de Janeiro) was a Brazilian mathematician. He spent most of his career at IMPA and is seen as the doyen of differential geometry in Brazil.
The best introduction in the fundamental topics of Riemannian Geometry. This book helped me a lot. M. P. do Carmo accomplished a very useful construction that most probably will help several generations of mathematicians as they advance in this topic.
The cover image goes hard af and I want a tattoo of it. But oh my god was this a hard read starting from 0 knowledge of manifolds. Lesson learned: Start by learning the topology before tacking on a metric.