Reply To: !
@Crackerjack_404 That’s good to hear. Your first successful solve will feel amazing.
Group theory is a really beautiful area which is ubiquitous in modern mathematics and in particular in modern cryptography. As for which book I would recommend, it really depends on how much maths you have seen. I personally learnt algebra from the first volume of Jacobson’s Basic Algebra, but I already knew some linear algebra and had enough free time that I could struggle with a hard book. The benefit of using Jacobson is that you can use the second volume to learn more advanced material, however the second volume is much more sophisticated than the first and arguably the presentation could have been improved by giving a more categorical view of things throughout volume 1, rather than just doing this in the second volume.
The other undergraduate level algebra text with which I am most familiar is Artin’s Algebra, which I used for a course at university. It is an okay book and (I seem to recall) introduces at the start the linear algebra which you will need. Both this and the above require a decent amount of mathematical maturity and I would not recommend them unless you have a decent amount of maths experience beyond the school curriculum, e.g. olympiad experience.
Whilst I can’t personally vouch for it, one of my algebra friends worked through Armstrong’s Groups and Symmetries when they were in high school and seemed to like it. Looking over the contents, it seems to be much slower paced and whilst it only covers Group theory it seems to have a good covering of the standard topics in an introductory course.
Really, your best bet is probably to ask Harry or someone else who is involved in maths outreach / pedagogy for a suggestion.