What is a good introduction in gradient flows in metric spaces? 
I know the book *Gradient flows: in metric spaces and in the space of probability measures by Luigi Ambrosio, Nicola Gigli and Giuseppe Savaré*, but is too hard for an introduction (for me).
I'm looking for something with a similar content.



Textbooks or notes on gradient flows in metric spaces
Here are some links to the online lecture notes which are hopefully more accessible than the book you mentioned:


* [Lecture Notes on Gradient Flows and Optimal Transport](https://arxiv.org/abs/1009.3737) by S. Daneri
* [An Introduction to Gradient Flows in Metric Spaces](http://igk.math.uni-bielefeld.de/study-materials/sm-cle-09.pdf) and 
[Introduction to Gradient Flows in Metric Spaces (II)](http://igk.math.uni-bielefeld.de/study-materials/notes-clement-part2.pdf) by P. Clément


