# What to read alongside with Hatcher Algebraic Topology

I know there are a few posts asking for references about algebraic topology textbooks. Still I have decided to open another one as I would like to ask a slightly different question: which textbook would you read to complement Hatcher's one?

I am more interested in texts which give a different insight or perspective on the same material (or a similar selection of material), rather than in maximally reducing the overlapping with Hatcher. Please give some reasons for your suggestions.

Moreover, beyond algebraic topology textbooks, are there any textbooks in related areas which would be profitable to read at this level - that is the level at which Hatcher's book is written?

In particular I would be interested in a text covering the algebraic material needed for algebraic topology. To give some examples of what I would like to see covered, the exercise on finding the Abelian groups $A$ which fit in the exact sequence $0\rightarrow \mathbb{Z}_{p^n}\rightarrow A\rightarrow \mathbb{Z}_{p^m}\rightarrow 0$ give me headaches (I am not asking for how to solve it here, but rather what to study to be able to confidently solve it). Or the remark "Since $\mathrm{Hom}(H,\mathbb{Z})$ is isomorphic to the free part of $H$ if $H$ is finitely generated" is not obvious to me (it would be in the case of vector spaces where I would translate it to a finite dimensional vector space and its dual are isomorphic).

EDIT: In response to an answer by Daniel Rust here are some more details on which parts of Hatcher I am interested in. I would like to get a better understanding of homology and cohomology (starting from the kind of presentation level you find in more elementary texts like Croom or Naber or Nakahara) and the way they are related. So in particular topics like the Universal Coefficients Theorem, Cup Product and Poincaré Duality.

Apart from my general interest in the topic, one of my aims is to better understand how the intersection matrix of a manifold is defined and practical way of computing it - in particular for 2-cycles inside a 4-manifold. While I know that in the smooth category many issues simplify, my feeling is that it pays off to learn about these concepts in their proper setting, i.e. the topological one.

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It's my experience that one doesn't usually 'read through Hatcher' at least not in the traditional sense of reading a book cover to cover. The material in Hatcher is simply too broad, ranging from basic introduction to algebraic topology all the way to very abstract homotopy theory. In my experience it's more of a reference book - after you've read the first chapter or two, you pick the right bits to read when you need them, often not in the order they're written.

The question in your last paragraph is more manageable as you're asking for extra material on the homological algebra covered in the text. My suggestion would be any of the classical texts on homological algebra such as Cartan-Eilenberg for a classical reference or any of a good range of modern texts which may be gentler introductions. There's a helpful thread here which covers books which might be of use.

I think if you are looking for complementary texts for other parts of Hatcher, you would get a better response if you made a separate question for each specific part. For instance "I'm looking for a more in-depth introduction to similar material on the surface theory covered by Hatcher - especially with regard to covering spaces." or "Hatcher glosses over some of the details in the section on Postnikov towers. Is there a reference with more details and possibly some examples?"

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I would recommend Weibel's "Introduction to Homological Algebra", just to reach a good level on the algebraic side following a rather modern treatment. As far as topology is concerned, after having read Hatcher a good step could be May's "Concise course in Algebraic Topology": it is far more "unified" than Hatcher and it provides a strong homotopical foundation to the subject. Finally, you can consider also to pass to the abstract side, of course after having understood the fundamental notions: I am thinking of abstract homotopy theory, which would give rise to a whole new post by itself!

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Some friend of mine used Massey's A basic course in algebraic topology along with Hatcher.

Personally I've find very fruitful using Spanier's Algebraic Topology book along side with Hatcher. This is a classical reference for algebraic topology and I really like it also because of its categorical taste (which is also a reason why many people don't like it).

About the other part of your question it seems to me that you're looking for a course in homological algebra. A good reference on the subject (at least in my personal opinion) is Hilton-Stammbach A course in homological algebra.

Hope this helps.

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I like Topology and Geometry by Glen E. Bredon, especially as a reference for cohomology and homology products.

I second Weibel's book on homological algebra, especially for the universal coefficient theorem.

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There are 2 big problems with Bredon to me, as promising as it looks initially: First of all,it's very poorly organized. But an even bigger problem is that it's not clear on the prerequisites-he uses category theory and basic homological algebra without warning or proper development in the text.I found that John Lee's INTRODUCTION TO TOPOLOGICAL MANIFOLDS has everything one needs to be able to read Bredon smmothly,so I strongly recommend working through that book first. – Mathemagician1234 May 3 '14 at 16:56
I'll put in a plug for my own book "Topology and Groupoids" especially as I got it printed myself to keep the price down. It is available on amazon. It is the only text at this level which takes seriously the role of groupoids as a model for 1-dimensional homotopy theory, which I publicised with the first 1968 edition. More details on pages.bangor.ac.uk/~mas010/topgpds.html . For a recent application, see arxiv.org/abs/1404.0556v3 . – Ronnie Brown Oct 14 '14 at 17:40