Textbooks, lecture notes, and articles from arXiv for undergraduate students I have found some interesting textbooks and articles on arXiv, such as the following one, that are accessible to an undergraduate student:

Course of linear algebra and multidimensional geometry, by
  Ruslan Sharipov.

My experience makes me believe that in arXiv there may be not only research papers, but also plenty of freely available interesting textbooks, lecture notes, and articles that can


*

*give insightful explanations of topics that are commonly found in an undergraduate degree program;

*but also enrich and broaden the mathematical culture of an undergraduate student.


Could you point out some good examples of such material?

I found this one a while ago:
Euclidean plane and its relatives;
a minimalist introduction
Anton Petrunin
https://arxiv.org/abs/1302.1630
btw...
Here is a "hack" you can do to look for books on arxiv. Do an advanced search for "these lecture notes" OR "this book" in the abstract. Show 200 results per page. Use your browser search now for "these lecture notes" and then for "this book" ont he book. arxiv's search can do exact match for author name, but not for text in the abstract, it seems. That is why the second step is needed with your browser search.
