Cohomology Operations and Applications in Homotopy Theory (Dover Books on Mathematics)

This doesn't make any sense, but somehow it's a terrible book and yet I like it a lot. If you need to learn the stuff that's in here, you don't have a lot of choices. It is very difficult to find well-written mathematics at this level; I would recommend this as a "best of al evils."

This is a good book for those who understand advanced algebraic topology. It is simplified as much as possible. If you are beginning to learn about gadgets like Steenrod algebra and some of the related topics in Algebraic topology, nothing can be better than this.

This is a great fast paced introduction to several structures in homotopy theory, by way of carefully explaining Steenrod Squares. You need to understand basic algebraic topology homology/cohomology/homotopy groups very well already, up to the point of obstruction theory and ideally Postnikov towers to take good advantage of what the book offers. The first chapter is an introduction to Eilenberg-MacLane spaces with a 1.5 page review of obstruction theory. The book is well written and pedagogical for the advanced student.

I've already red many books and articles about Steenrod Operations but I never understood them. With this book all was clear, thank you very much sir Mosher